Rooms or places seem to be the correct term as one of Apostle John's disciples said the following:
Three places he has for his righteous, City of God, Paradise and Heaven above. Based all this on 30, 60 and 100 of those brought to know the Lord
Isa 65:17 For, behold, I create new heavens and a new earth: and the former shall not be remembered, nor come into mind.
2Pe 3:7 But the heavens and the earth, which are now, by the same word are kept in store, reserved unto fire against the day of judgment and perdition of ungodly men.
2Pe 3:10 But the day of the Lord will come as a thief in the night; in the which the heavens shall pass away with a great noise, and the elements shall melt with fervent heat, the earth also and the works that are therein shall be burned up.
2Pe 3:12 Looking for and hasting unto the coming of the day of God, wherein the heavens being on fire shall be dissolved, and the elements shall melt with fervent heat?
2Pe 3:13 Nevertheless we, according to his promise, look for new heavens and a new earth, wherein dwelleth righteousness.
Joh 14:2 In my Father's house are many mansions: if it were not so, I would have told you. I go to prepare a place for you.
Joh 14:3 And if I go and prepare a place for you, I will come again, and receive you unto myself; that where I am, there ye may be also.
Rev 21:1 And I saw a new heaven and a new earth: for the first heaven and the first earth were passed away; and there was no more sea.
Rev 21:2 And I John saw the holy city, new Jerusalem, coming down from God out of heaven, prepared as a bride adorned for her husband.
Rev 21:3 And I heard a great voice out of heaven saying, Behold, the tabernacle of God is with men, and he will dwell with them, and they shall be his people, and God himself shall be with them, and be their God.
Rev 21:4 And God shall wipe away all tears from their eyes; and there shall be no more death, neither sorrow, nor crying, neither shall there be any more pain: for the former things are passed away.
Rev 21:5 And he that sat upon the throne said, Behold, I make all things new. And he said unto me, Write: for these words are true and faithful.
There is only one place where all the saints will dwell as their final destination the New Jerusalem.
Mat 20:2 And when he had agreed with the labourers for a penny a day, he sent them into his vineyard.
Mat 20:3 And he went out about the third hour, and saw others standing idle in the marketplace,
Mat 20:4 And said unto them; Go ye also into the vineyard, and whatsoever is right I will give you. And they went their way.
Mat 20:5 Again he went out about the sixth and ninth hour, and did likewise.
Mat 20:9 And when they came that were hired about the eleventh hour, they received every man a penny.
Mat 20:10 But when the first came, they supposed that they should have received more; and they likewise received every man a penny.
Mat 20:11 And when they had received it, they murmured against the goodman of the house,
Mat 20:12 Saying, These last have wrought but one hour, and thou hast made them equal unto us, which have borne the burden and heat of the day.
Mat 20:13 But he answered one of them, and said, Friend, I do thee no wrong: didst not thou agree with me for a penny?
There is not different levels of salvation to dwell in 3 different places but they will all dwell in one place.
Mat 5:17 Think not that I am come to destroy the law, or the prophets: I am not come to destroy, but to fulfil.
Mat 5:18 For verily I say unto you, Till heaven and earth pass, one jot or one tittle shall in no wise pass from the law, till all be fulfilled.
Zec 14:9 And the LORD shall be king over all the earth: in that day shall there be one LORD, and his name one.
Zec 14:16 And it shall come to pass, that every one that is left of all the nations which came against Jerusalem shall even go up from year to year to worship the King, the LORD of hosts, and to keep the feast of tabernacles.
Jesus came to fulfill the law which includes the offices of Israel.
But He has not fulfilled the role of King on earth yet because He came as a humble servant.
And it must be done on earth.
That is what the millennial reign is about.
When the reign is over the law is fulfilled and haven and earth shall pass away.
Which it is done by fire for all sin must be purged with fire.
Which heaven and earth has been tainted with sin.
Then all the saints will go to the place Jesus prepared the New Jerusalem where sin has never been and sin will never be.
And the saints and angels will remember nothing prior to that for it is associated with sin.
Joh 14:2 In my Father's house are many mansions: if it were not so, I would have told you. I go to prepare a place for you.
Mansion
monē
mon-ay'
From G3306; a staying, that is, residence (the act or the place): - abode, mansion.
Jesus could be saying that there is much room in heaven to accommodate every person that saved.
There is not a sign that says occupancy 2,000,000 but it can hold all people saved.