Something that has bugged me for a while (and the answer may well be “we can’t know yet, prophecy is tricky till it’s fulfilled”):
Jesus says, several times, that the Second Coming could be at any moment (or at least that’s what it seems to mean). But there is also prophecy about a mass conversion of Israel after “the times of the Gentiles” – “all Israel shall be saved”. So how come we can’t know, since that clearly has not yet happened, that the Second Coming is not that imminent? (Same goes for the Antichrist, I guess… but is it quite so clear that the Antichrist will be obviously the Antichrist? While a mass conversion of Israel/Judaism to the Church could hardly be missed.)
Have you considered the possibility that Rom 11 isn’t saying anything about a mass conversion of Israel?
“I want you to understand this mystery, brethren: a hardening has come upon part of Israel, until the full number of the Gentiles come in, and so all Israel will be saved; as it is written, “The Deliverer will come from Zion, he will banish ungodliness from Jacob” "and this will be my covenant with them when I take away their sins” (Rom. 11:25-27).
What if the last Gentile comes in at the very last moment on the very last day of time itself? That would mean that Jews would be hardened until the very end of time.
But, I think Paul is actually talking about the manner of salvation for the Jews and not numbers or timing. A remnant of Israel will be saved by grace just like the gentile. If they do not persist in their unbelief they will be grafted in. Meaning, “all Israel” would be the cumulative total of Jews saved by grace until the very last day. Could there be a mass converstion? Sure! But I don’t think that Rom 11 can be used to argue the point that it must happen. It’s about the manner of salvation (grace), rather than the number or timing.
**And Isaiah cries out concerning Israel, “Though the number of the Israelites were like the sand of the sea, only a remnant will be saved; for decisively and quickly will the Lord execute sentence upon the earth.” (Rom 9:27-28)
Now I am speaking to you Gentiles. Inasmuch then as I am the apostle to the Gentiles, I glory in my ministry in order to make my race jealous and thus save some of them. For if their rejection is the reconciliation of the world, what will their acceptance be but life from the dead? (Rom 11:13-15)
Just as you once disobeyed God but have now received mercy because of their disobedience, so they have now disobeyed in order that, by virtue of the mercy shown to you, they too may (now) receive mercy. For God delivered all to disobedience, that he might have mercy upon all. (Rom 11:30-32)**
Does that make sense?
Alternatively, “all Israel” could also be viewed as the sum total of both Jews and Gentiles who will be saved.