Would it be only the availability of the HOly Spirit to everyone?
As strange as this may initially sound, I have to say "no" and here's why:
I Corinthians chapter 10
1] Moreover, brethren, I would not that ye should be ignorant, how that all our fathers were under the cloud, and all passed through the sea;
[2] And were all baptized unto Moses in the cloud and in the sea;
[3] And did all eat the same spiritual meat;
[4] And did all drink the same spiritual drink: for they drank of that spiritual Rock that followed them: and that Rock was Christ.
Do you recall the two different occasions during the children of Israel's wilderness journeys where they "thirsted" and God gave them water to drink from the rock? Here are the two accounts:
Exodus chapter 17
[1] And all the congregation of the children of Israel journeyed from the wilderness of Sin, after their journeys, according to the commandment of the LORD, and pitched in Rephidim: and there was no water for the people to drink.
[2] Wherefore the people did chide with Moses, and said, Give us water that we may drink. And Moses said unto them, Why chide ye with me? wherefore do ye tempt the LORD?
[3] And the people thirsted there for water; and the people murmured against Moses, and said, Wherefore is this that thou hast brought us up out of Egypt, to kill us and our children and our cattle with thirst?
[4] And Moses cried unto the LORD, saying, What shall I do unto this people? they be almost ready to stone me.
[5] And the LORD said unto Moses, Go on before the people, and take with thee of the elders of Israel; and thy rod, wherewith thou smotest the river, take in thine hand, and go.
[6] Behold, I will stand before thee there upon the rock in Horeb; and thou shalt smite the rock, and there shall come water out of it, that the people may drink. And Moses did so in the sight of the elders of Israel.
[7] And he called the name of the place Massah, and Meribah, because of the chiding of the children of Israel, and because they tempted the LORD, saying, Is the LORD among us, or not?
The first time that the children of Israel chided with Moses in relation to their "thirst", God commanded Moses to "smite the rock and there shall come water out of it that the people may drink". Keep in mind that we just read in I Corinthians chapter 10 that this "Rock that followed them WAS CHRIST" and that "they all drank the same SPIRITUAL DRINK". Well, what does that tell us? It tells us that when the rock was smitten it was a "type" of Christ being crucified and that the water which came out truly was "spiritual drink" in that it was a "type" of the Holy Spirit WHICH GOD WANTED ALL OF THE CHILDREN OF ISRAEL TO PARTAKE OF. Remember, Jesus also spoke to the Samaritan woman at the well in relation to this same type of "living water":
John chapter 4
5] Then cometh he to a city of Samaria, which is called Sychar, near to the parcel of ground that Jacob gave to his son Joseph.
[6] Now Jacob's well was there. Jesus therefore, being wearied with his journey, sat thus on the well: and it was about the sixth hour.
[7] There cometh a woman of Samaria to draw water: Jesus saith unto her, Give me to drink.
[8] (For his disciples were gone away unto the city to buy meat.)
[9] Then saith the woman of Samaria unto him, How is it that thou, being a Jew, askest drink of me, which am a woman of Samaria? for the Jews have no dealings with the Samaritans.
[10] Jesus answered and said unto her, If thou knewest the gift of God, and who it is that saith to thee, Give me to drink; thou wouldest have asked of him, and he would have given thee living water.
[11] The woman saith unto him, Sir, thou hast nothing to draw with, and the well is deep: from whence then hast thou that living water?
[12] Art thou greater than our father Jacob, which gave us the well, and drank thereof himself, and his children, and his cattle?
[13] Jesus answered and said unto her, Whosoever drinketh of this water shall thirst again:
[14] But whosoever drinketh of the water that I shall give him shall never thirst; but the water that I shall give him shall be in him a well of water springing up into everlasting life.
Well, what happened the second time that the chidren of Israel chided with Moses in relation to their "thirst"?
Numbers chapter 20
[2] And there was no water for the congregation: and they gathered themselves together against Moses and against Aaron.
[3] And the people chode with Moses, and spake, saying, Would God that we had died when our brethren died before the LORD!
[4] And why have ye brought up the congregation of the LORD into this wilderness, that we and our cattle should die there?
[5] And wherefore have ye made us to come up out of Egypt, to bring us in unto this evil place? it is no place of seed, or of figs, or of vines, or of pomegranates; neither is there any water to drink.
[6] And Moses and Aaron went from the presence of the assembly unto the door of the tabernacle of the congregation, and they fell upon their faces: and the glory of the LORD appeared unto them.
[7] And the LORD spake unto Moses, saying,
[8] Take the rod, and gather thou the assembly together, thou, and Aaron thy brother, and speak ye unto the rock before their eyes; and it shall give forth his water, and thou shalt bring forth to them water out of the rock: so thou shalt give the congregation and their beasts drink.
[9] And Moses took the rod from before the LORD, as he commanded him.
[10] And Moses and Aaron gathered the congregation together before the rock, and he said unto them, Hear now, ye rebels; must we fetch you water out of this rock?
[11] And Moses lifted up his hand, and with his rod he smote the rock twice: and the water came out abundantly, and the congregation drank, and their beasts also.
[12] And the LORD spake unto Moses and Aaron, Because ye believed me not, to sanctify me in the eyes of the children of Israel, therefore ye shall not bring this congregation into the land which I have given them.
[13] This is the water of Meribah; because the children of Israel strove with the LORD, and he was sanctified in them.
On this second occasion, God commanded Moses to "speak unto the rock befofe their eyes and it shall give forth his water", but Moses disobeyed and "smote the rock twice" and he was forbidden by God to step foot within "the promised land" for this act of disobedience. Why was God so angry with Moses that He forbid him entrance into "the promised land"? Well, again, remember that "the Rock that followed them WAS CHRIST", so when God instructed Moses to "speak unto the rock before their eyes and it shall give forth his water", He was, in "type", instructing Moses to teach the children of Israel to SPEAK TO CHRIST FOR ANY ADDITIONAL "WATER" OR "SPIRITUAL DRINK". IOW, like the children of Israel, we all initially receive our own "spiritual drink" via faith in the "smitten Rock" or via faith in the crucified Christ. For any subsequent "drinks", however, we need to "speak to the rock" or have a prayer life with Christ in order to obtain more "spiritual drink". As such, when Moses broke the "type" and "smote the rock twice", God was very angry with him. Remember, scripture tells us that Christ will not be "crucified afresh" (Hebrews 6:6) and, in "type", Moses taught the opposite by smiting the rock twice. Anyhow, I said all of that to say this...
It has always been God's desire that EVERYBODY "drink the same SPIRITUAL DRINK" from the Rock OF CHRIST.
John chapter 7
[37] In the last day, that great day of the feast, Jesus stood and cried, saying, If any man thirst, let him come unto me, and drink.
[38] He that believeth on me, as the scripture hath said, out of his belly shall flow rivers of living water.
[39] (But this spake he of the Spirit, which they that believe on him should receive: for the Holy Ghost was not yet given; because that Jesus was not yet glorified.)
Now, why do you suppose that Jesus said that? When He told people who "thirsted" to "come unto me and drink", is it possible that He was alluding back to Himself being "the Rock that followed them" in the wilderness journeys from which people received "spiritual drink"? Personally, I'm convinced that that is exactly what Jesus was doing. In any case, again, my point is that Jesus has always wanted EVERYBODY to come to Him and "drink" and here this "drink" was specifically likened to "the Holy Ghost". Please also consider that in our opening text from I Corinthians chapter 10 we read how that "ALL OUR FATHERS were under the cloud" and how that they "were ALL baptized unto Moses", a "type" of Christ himself, "in the cloud". IOW, again, in "type", they all received a Holy Ghost baptism which is what "the cloud" represents.
Having said all of that, Peter did say that what transpired on the day of Pentecost was a fulfillment of what Joel had prophesied, but, again, it has always been God's desire for EVERYBODY to be saved and indwelt by His Spirit.
I hope that this helps to answer your question.