The 144,000 people are Jews for God has a plan for them.
6When they therefore were come together, they asked of him, saying, Lord, wilt thou at this time restore again the kingdom to Israel?
7And he said unto them, It is not for you to know the times or the seasons, which the Father hath put in his own power(Acts 1:6-7).
The disciples asked Jesus if He was going to restore the kingdom to them at that time,and Jesus said for them to not worry about it but go about preaching the Gospel.
The Jews knew that God would restore the kingdom to them one day and Jesus did not deny that but said it will happen later.
1The word that came to Jeremiah from the LORD, saying,
2Thus speaketh the LORD God of Israel, saying, Write thee all the words that I have spoken unto thee in a book.
3For, lo, the days come, saith the LORD, that I will bring again the captivity of my people Israel and Judah, saith the LORD: and I will cause them to return to the land that I gave to their fathers, and they shall possess it.
4And these are the words that the LORD spake concerning Israel and concerning Judah.
5For thus saith the LORD; We have heard a voice of trembling, of fear, and not of peace.
6Ask ye now, and see whether a man doth travail with child? wherefore do I see every man with his hands on his loins, as a woman in travail, and all faces are turned into paleness?
7Alas! for that day is great, so that none is like it: it is even the time of Jacob's trouble, but he shall be saved out of it.
8For it shall come to pass in that day, saith the LORD of hosts, that I will break his yoke from off thy neck, and will burst thy bonds, and strangers shall no more serve themselves of him:
9But they shall serve the LORD their God, and David their king, whom I will raise up unto them.
10Therefore fear thou not, O my servant Jacob, saith the LORD; neither be dismayed, O Israel: for, lo, I will save thee from afar, and thy seed from the land of their captivity; and Jacob shall return, and shall be in rest, and be quiet, and none shall make him afraid.
11For I am with thee, saith the LORD, to save thee: though I make a full end of all nations whither I have scattered thee, yet I will not make a full end of thee: but I will correct thee in measure, and will not leave thee altogether unpunished(Jeremiah 30:1-11).
God said He will bring the Jews from the nation where they were scattered and bring them to their land,and cause all Gentile nations to fall,but Israel will not fall,which will be when God restores the kingdom to them.
This prophesy has not come to pass for there are still Gentile governments in operation,and Israel is not the only nation ruling.
25For I would not, brethren, that ye should be ignorant of this mystery, lest ye should be wise in your own conceits; that blindness in part is happened to Israel, until the fulness of the Gentiles be come in.
26And so all Israel shall be saved: as it is written, There shall come out of Sion the Deliverer, and shall turn away ungodliness from Jacob:
27For this is my covenant unto them, when I shall take away their sins(Romans 11:25-27).
All Israel shall be saved which is physical as a nation where all Gentile nations shall fall,which is a prophesy to come.