It is interesting reading all of the different perspectives. Thanks to everyone who has commented.
Just thought I would note some of my current “speculations”
1 At this stage, some passages in the bible that I used to think were about the future, I now see as speaking of life here and now or about events occurring in AD 70.
But 1 Cor 15, in speaking of death and resurrection, and our earthly, perishable, weak, natural, mortal bodies being changed to heavenly, imperishable, powerful, spiritual, immortal bodies in the twinkling of an eye, at the sound of the last trumpet (as in 1 Thes 4:16) - still sounds to me like Paul is speaking of our resurrection bodies after death, rather than something at 70 AD. But hey, I could be wrong. and I admit that I have not done enough thinking on this subject.
2 1 Cor 15 is only referring to believers receiving immortal bodies and doesn’t refer to unbelievers. (Thanks Paidion).
3 Believers will be given immortal, imperishable bodies when Christ returns. Does this still leave the possibility that God will have more work to do in us for such things as making us more mature (thanks Cindy, Steve), or for us to be properly reconciled to those we have wronged in this life? Perhaps so.
Cindy, you said
I was wondering if you might elaborate on why you feel certain of this?
4 Some people will be condemned at the judgement (after death) that Heb 9:27 refers to. But their condemnation is not final. God will work to bring those who are condemned to life in Christ. For some unbelievers this may be a long process.
5 Regarding those who die while still unbelievers - when will they receive imperishable bodies?? Perhaps when they repent after death?? I don’t know - and I am not sure that the bible really tells us this detail. I can see that the ultrauniversalist position is much tidier on this question (thanks Geoffrey), but raises other questions for me at this stage.