There is not one single iota, jot, or tittle, about there not being a future for Israel.
That we would all agree - Israel has been rejoicing in the realisation of God's promises through her Messiah since Pentecost. Many thousands of Jews came to a living, saving faith in Jesus from all round the Roman Empire & beyond as recorded in Acts, & there is no reason to suppose they stopped believing in the following generations down the millennia.
I certainly do not think that God abandoned Abraham's descendants for 60-100 generations as seems to be implied by the OP. Christian Jews are not identifiable as Jews - they've been long identified simply as Christians & share all God's Covenant promises with all God's redeemed people.
As God declared:
Deut. 7:9 “Therefore know that the Lord your God, He is God, the faithful God who keeps covenant and mercy for a thousand generations with those who love Him and keep His commandments; 10 and He repays those who hate Him to their face, to destroy them. He will not be slack with him who hates Him; He will repay him to his face.
But did the Jewish believers maintain their separate Jewish identity? At first they reluctantly associated with Gentile believers as they were guided by the Holy Spirit. Then into spiritual unity with them, though warning the Gentiles not to give offence to their Jewish brothers. (Acts 15.)
It would seem from Acts that the Jewish believers were excluded from the synagogues by the unbelieving Jews. e.g.
Acts 18:5 When Silas and Timothy had come from Macedonia, Paul was compelled by the Spirit, and testified to the Jews thatJesus is the Christ. 6 But when they opposed him and blasphemed, he shook his garments and said to them, “Your blood be upon your own heads; I am clean. From now on I will go to the Gentiles.” 7 And he departed from there and entered the house of a certain man named Justus, one who worshiped God, whose house was next door to the synagogue. 8 Then Crispus, the ruler of the synagogue, believed on the Lord with all his household. And many of the Corinthians, hearing, believed and were baptized.
The attempt by the Christian Pharisees to maintain a separate Jewish church with Gentiles becoming Jewish proselytes was rejected at the Acts 15 conference, though it seems, e.g. from Gal. 2 that James did not follow through the decision & sought to maintain separation. It would have been easy to maintain a Jewish congregation in Jerusalem, but that would would not be possible elsewhere.
Percho said:
Let me ask a question.
Hosea 1:9,10 Then said
God, Call his name Loammi: for
ye are not my people, and I will not be your
God. Yet the number of the children of Israel shall be as the sand of the sea, which cannot be measured nor numbered; and it shall come to pass,
that in the place where it was said unto
them,
Ye are not my people,
there it shall be said unto
them,
Yeare the sons of the living God.
Did Paul believe, "them," were no longer, "them"? Is it God who is electing his children as believers or we electing to be his children by our work of believing?
Both Peter & Paul claim the Hosea prophecy applies to the Gentile believers, without excluding Jewish believers.
Rom. 9:22 What if God, wanting to show His wrath and to make His power known, endured with much longsuffering the vessels of wrath prepared for destruction, 23 and that He might make known the riches of His glory on the vessels of mercy, which He had prepared beforehand for glory, 24 even us whom He called, not of the Jews only, but also of the Gentiles?
25 As He says also in Hosea:
“I will call them My people, who were not My people, And her beloved, who was not beloved.”
26 “And it shall come to pass in the place where it was said to them,
‘You are not My people,’ There they shall be called sons of the living God.”
1 Peter 2:7 Therefore, to you who believe, He is precious; but to those who are disobedient,
“The stone which the builders rejected Has become the chief cornerstone,”
8 and “A stone of stumbling And a rock of offense.”
They stumble, being disobedient to the word, to which they also were appointed.
9 But you are a chosen generation, a royal priesthood, a holy nation, His own special people, that you may proclaim the praises of Him who called you out of darkness into His marvelous light; 10 who once were not a people but are now the people of God, who had not obtained mercy but now have obtained mercy.
Of course the Jews, the descendants of Abraham are in no way rejected. They are welcomed by the Gospel of salvation through the LORD Jesus Christ.
There is still the question as to whether those who claim to be Jews, but reject the Gospel can claim the Old Covenant promises, particularly as the Old Covenant came to an end:
Heb. 8:13 In that He says, “A new covenant,” He has made the first obsolete. Now what is becoming obsolete and growing old is ready to vanish away.
From John the baptist onwards, claims to privilege on the basis of descent from Abraham were rejected. Circumcision of the heart was recognised by Moses & the prophets. Deut. 10:16, 30:6, Jer. 4:4.
And with the Gospel, the promised land becomes the New Heaven & New Earth, a much more glorious & vast territory. The patriarchs understood this:
Heb. 11:8 By faith Abraham obeyed when he was called to go out to the place which he would receive as an inheritance. And he went out, not knowing where he was going. 9 By faith he dwelt in the land of promise as in a foreign country, dwelling in tents with Isaac and Jacob, the heirs with him of the same promise; 10 for he waited for the city which has foundations, whose builder and maker is God.
......
13 These all died in faith, not having received the promises, but having seen them afar off were assured of them,embraced them and confessed that they were strangers and pilgrims on the earth. 14 For those who say such things declare plainly that they seek a homeland. 15 And truly if they had called to mind that country from which they had come out, they would have had opportunity to return. 16 But now they desire a better, that is, a heavenly country. Therefore God is not ashamed to be called their God, for He has prepared a city for them.
2 Peter 3:10 But the day of the Lord will come as a thief in the night, in which the heavens will pass away with a great noise, and the elements will melt with fervent heat; both the earth and the works that are in it will be burned up. 11 Therefore, since all these things will be dissolved, what manner of persons ought you to be in holy conduct and godliness, 12 looking for and hastening the coming of the day of God, because of which the heavens will be dissolved, being on fire, and the elements will melt with fervent heat? 13 Nevertheless we, according to His promise, look for new heavens and a new earth in which righteousness dwells.
God can fulfill all his OC promises to Abraham by his Seed, the LORD Jesus Christ, without separating out ethnic Jews for an earthly kingdom.
Gal. 3 makes that clear.