I’ve always thought the JW argument for two destinies is a pretty good one - maybe, but I think a pretty good argument could be made against, too.
Jews (nation of Israel) were chosen, according to the NT & OT. They were God's property. Strict punishments were enforced for disobedience, e.g. stoning for gays who had a sexual relationship and even for children who cursed/mocked their parents. The mainstream Christian argument goes that this was necessary to make the Jews see the need for the Messiah. Fleshly Israel lived on earth; spiritual Israel lived in peoples' hearts and their hope was also spiritual (heavenly).
It's fascinating that Jesus never said explicitly that the 'other sheep' had an earthly hope. <---- this is correct, right?
Neither did any of the early Christians say this - not Paul, nor John, etc.