Abraham had two covenants. The first was the land covenant and descendants. Abraham's "great nation". The second includes the establishing of the blessing through Abraham's seed, which Hebrews says is Jesus. The promise made following this, when Abraham went to sacrifice Isaac, speaks directly to the world, to include Gentiles, those outside of the covenant, would also be blessed in Christ, Abraham's seed. So I can take it that you are speaking solely to Abraham's two covenants.
Then there is the Mosaic covenant, a covenant that would be a covenant of salvation. Salvation through keeping the law, being God's people, and obeying His commands. All the way up to Jesus time, it was believed that EVERY Jew entered into the Kingdom solely because of the Mosaic covenant. No Jews go into "Gehenna". An interesting point made by the author I read (messianic Jew) who spoke to this said it created a quandary. The rabbis taught that every Christian went to Gehenna, so what about Jewish (none go to Gehenna) Christians (all go to Gehenna).
The reason why God will give Israel, and Israel only, a new covenant is because Israel violated the Mosaic covenant. This is not a replacement for the Abrahamic covenants. Though Paul would argue that circumcision is no longer a requirement, and is an impediment. (By being circumcised, one places themselves under the Law.) The new covenant comes when God reconciles with Israel. (Revelation 19; Zechariah (I don't remember the exact chapter off hand.) Jesus returns, and they recognize Him, and God opens fountains of regeneration and rivers of repentance. All Israel (that survives until this time) is saved. I believe the elect, the remnant that God kept for Himself that are not yet saved, will be all that remains, and God saves at this time. They receive a new covenant, a fulfillment of the Abrahamic covenant with the land promise, and at that time, in line with the question of the disciples before Jesus left, Jesus will return the Kingdom to Israel. That question did not cease to be relevant, because Jesus never said it wouldn't happen. All He said to the disciples who asked if He was going to do it NOW, was that it wasn't for them to know when. That is the Father's domain. So, a question for you, if the disciples were to keep asking this question, when would His answer change to YES?