“All of Israel” ... is ... all who are alive then ...
It would be the same today, if I said “all of Israel” in some statement to you right now — I’m definitely not talking about the dead people ... LOL ...
SO ... yes ... ALL of Israel will be saved on the day the Messiah of Israel returns!
According to the Scriptures all of Israel who are alive, that is, who are left, is 1/3 of those living in the land.