Hi again Logos1, I would disagree that God would have to put Israel back under their old covenant to keep His covenant promises to them although they had their chance to enter those promises as demonstrated in the Book of Acts.
Acts 3
12 And when Peter saw it, he answered unto the people, Ye men of Israel, why marvel ye at this? or why look ye so earnestly on us, as though by our own power or holiness we had made this man to walk?
13 The God of Abraham, and of Isaac, and of Jacob, the God of our fathers, hath glorified his Son Jesus; whom ye delivered up, and denied him in the presence of Pilate, when he was determined to let him go.
14 But ye denied the Holy One and the Just, and desired a murderer to be granted unto you;
15 And killed the Prince of life, whom God hath raised from the dead; whereof we are witnesses.
16 And his name through faith in his name hath made this man strong, whom ye see and know: yea, the faith which is by him hath given him this perfect soundness in the presence of you all.
17 And now, brethren, I wot that through ignorance ye did it, as did also your rulers.
18 But those things, which God before had shewed by the mouth of all his prophets, that Christ should suffer, he hath so fulfilled.
19 Repent ye (men of Israel) therefore, and be converted, that your sins may be blotted out, when the times of refreshing shall come from the presence of the Lord;
20 And he shall send Jesus Christ, which before was preached unto you:
21 Whom the heaven must receive until the times of restitution of all things, which God hath spoken by the mouth of all his holy prophets since the world began.
13 The God of Abraham, and of Isaac, and of Jacob, the God of our fathers, hath glorified his Son Jesus; whom ye delivered up, and denied him in the presence of Pilate, when he was determined to let him go.
14 But ye denied the Holy One and the Just, and desired a murderer to be granted unto you;
15 And killed the Prince of life, whom God hath raised from the dead; whereof we are witnesses.
16 And his name through faith in his name hath made this man strong, whom ye see and know: yea, the faith which is by him hath given him this perfect soundness in the presence of you all.
17 And now, brethren, I wot that through ignorance ye did it, as did also your rulers.
18 But those things, which God before had shewed by the mouth of all his prophets, that Christ should suffer, he hath so fulfilled.
19 Repent ye (men of Israel) therefore, and be converted, that your sins may be blotted out, when the times of refreshing shall come from the presence of the Lord;
20 And he shall send Jesus Christ, which before was preached unto you:
21 Whom the heaven must receive until the times of restitution of all things, which God hath spoken by the mouth of all his holy prophets since the world began.
Obviously they continued in their rebellion against Christ's apostles until:
Acts 13
46 Then Paul and Barnabas waxed bold, and said, It was necessary that the word of God should first have been spoken to you: but seeing ye put it from you, and judge yourselves unworthy of everlasting life, lo, we turn to the Gentiles.
47 For so hath the Lord commanded us, saying, I have set thee to be a light of the Gentiles, that thou shouldest be for salvation unto the ends of the earth.
48 And when the Gentiles heard this, they were glad, and glorified the word of the Lord: and as many as were ordained to eternal life believed.
46 Then Paul and Barnabas waxed bold, and said, It was necessary that the word of God should first have been spoken to you: but seeing ye put it from you, and judge yourselves unworthy of everlasting life, lo, we turn to the Gentiles.
47 For so hath the Lord commanded us, saying, I have set thee to be a light of the Gentiles, that thou shouldest be for salvation unto the ends of the earth.
48 And when the Gentiles heard this, they were glad, and glorified the word of the Lord: and as many as were ordained to eternal life believed.
But that does not negate the scriptural fact of Romans 11
Romans 11
24 For if thou wert cut out of the olive tree which is wild by nature, and wert graffed contrary to nature into a good olive tree: how much more shall these, which be the natural branches, be graffed into their own olive tree?
25 For 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.
26 And 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:
27 For this is my covenant unto them, when I shall take away their sins.
28 As concerning the gospel, they are enemies for your sakes: but as touching the election, they are beloved for the fathers' sakes.
29 For the gifts and calling of God are without repentance.
24 For if thou wert cut out of the olive tree which is wild by nature, and wert graffed contrary to nature into a good olive tree: how much more shall these, which be the natural branches, be graffed into their own olive tree?
25 For 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.
26 And 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:
27 For this is my covenant unto them, when I shall take away their sins.
28 As concerning the gospel, they are enemies for your sakes: but as touching the election, they are beloved for the fathers' sakes.
29 For the gifts and calling of God are without repentance.
In the Matthew 24 passage the times of the Gentiles will endure until the those times are fulfilled. As previously stated Jerusalem is still "trodden down" by the Gentiles. The restoration of verses 26 and 27 is yet to be fulfilled.
This restoration was also promised in the OT:
Jeremiah 31
31 Behold, the days come, saith the LORD, that I will make a new covenant with the house of Israel, and with the house of Judah:
32 Not according to the covenant that I made with their fathers in the day that I took them by the hand to bring them out of the land of Egypt; which my covenant they brake, although I was an husband unto them, saith the LORD:
33 But this shall be the covenant that I will make with the house of Israel; After those days, saith the LORD, I will put my law in their inward parts, and write it in their hearts; and will be their God, and they shall be my people.
31 Behold, the days come, saith the LORD, that I will make a new covenant with the house of Israel, and with the house of Judah:
32 Not according to the covenant that I made with their fathers in the day that I took them by the hand to bring them out of the land of Egypt; which my covenant they brake, although I was an husband unto them, saith the LORD:
33 But this shall be the covenant that I will make with the house of Israel; After those days, saith the LORD, I will put my law in their inward parts, and write it in their hearts; and will be their God, and they shall be my people.
I take Jeremiah 31 as the future fulfilment of Romans 11:26-29 even though as a nation they are presently still in rebellion.
That the entirety of the Abrahamic covenant be fulfilled.
The promises of God are without repentance.
The promises of God are without repentance.
Israel failed and has yet to repent but God can and will do His part in the keeping of the promises made to Old Covenant Israel without putting them back under the Old.
So my answer would be that the Old Covenant promises to Israel will be fulfilled during the millennium (redeemed Israel, the "sealed" 144,000 of the Revelation), though the Old Covenant itself has been abrogated, God will keep His word to Abraham Isaac and Jacob (aka Israel).
HankD