If your only concern is for those that have passed away before Jesus return for them again, well I think it might be the case of them being in some "limbo place", similar to how the OT saints were supposedly in Abraham's bosom, a kind of paradise, before Jesus went to preach to them after he was crucified.
But we don't know how exactly that is gonna happen. If Paul stated that "all Israel will be saved because God's covenant with Abraham is irrevocable, I can accept that to be the truth. The Jews can really thank their father Abraham for that.
For I could wish that myself were accursed from Christ for my brethren, my kinsmen
according to the flesh. Who are Israelite's, to whom pertain the adoption and the glory
and the covenants and the giving of the law and the service of God and the promises
Whose are the fathers and of whom as concerning the flesh Christ came
who is over all
God blessed forever Amen. Not as though the word of God hath taken none effect.
For they are not all Israel which are of Israel. Neither because they are the seed of Abraham
are they all children but in Isaac shall thy seed be counted.
Rom 9: 3- 7 KJV
Esaias also cried concerning Israel. Though the number of the Children
of Israel be as the sand of the sea
a remnant shall be saved.
Rom 9:27 KJV
And think not to say within yourselves We have Abraham to our
Father for I say to you that God is able of these stones to raise up
children of Abraham. And now the axe is laid unto the root of the trees
therefore every tree which
bringeth not good fruit is hewn down and
cast into the fire.
Matt 3: 9-10 KJV
Verily I say unto you I have not found so great faith no not in Israel
And I say unto you that many shall come from the East and West and
and shall sit down with Abraham and Isaac and Jacob in the kingdom of
Heaven.
But the children of the kingdom shall be cast out into outer
darkness there shall be weeping and gnashing of teeth.
Matt 8: 10-12 KJV
''All Israel will be saved'' is trotted out by every pre Trib Dispensationalist because the notion of a separate path to salvation for
Jews and Gentiles is the fundamental root of in their eschatological system. A system that imposes interpretations on scripture
takes verses out of context and only compares scripture with scripture when it suits them.
A remnant of Israel will be saved not all. Those who believe in Christ and have the faith of Abraham will be saved. Many others
living or dead at the time of the second coming wont be.