The prestigious The Pauline Epistles (Oxford Bible Commentary) published by Oxford University Press is clear that Paul expects to be alive when Christ returns.
What is the evidence for this?
Here is an example from 1 Corinthians 15:50-54 :
What I am saying, brothers and sisters,[a] is this: flesh and blood cannot inherit the kingdom of God, nor does the perishable inherit the imperishable. 51 Listen, I will tell you a mystery! We will not all die,[b] but we will all be changed, 52 in a moment, in the twinkling of an eye, at the last trumpet. For the trumpet will sound, and the dead will be raised imperishable, and we will be changed. 53 For this perishable body must put on imperishability, and this mortal body must put on immortality. 54 When this perishable body puts on imperishability, and this mortal body puts on immortality, then the saying that is written will be fulfilled: “Death has been swallowed up in victory.”
a. 1 Corinthians 15:50 Gk brothers
b. 1 Corinthians 15:51 Gk fall asleep
Note the contrast between “the dead” and “we“. Paul seems to think that Jesus will come in his own generation.
The Pauline Epistles (Oxford Bible Commentary) comments on this passage by Paul (p. 124):
The chapter finishes with a triumphant declaration of the hope on which the whole Christian faith depends, a ‘mystery’ which makes sense of the present in light of the future (vv. 51-8). Although not all will die first (‘sleep’), it is certainly the case that all will be changed, that is, our perishable selves will become imperishable and fit for the ‘kingdom of God’ (v.50). Using traditional apocalyptic imagery, Paul imagines this great change taking place ‘at the last trumpet’ (v. 52).
Since he supposes here that he and his generation will be alive at this end-point in history (cf. 7:29-31; 1 Thess 4:15, 17), he distinguishes between ‘the dead’ who will be raised in the new imperishable state and ‘we’ who will be changed from a mortal life to a new immortal state (vv. 52-4).
2000 years later Paul is proved wrong by the passage of time. He believed he was commissioned by God to preach the Truth to the gentiles.
But this is impossible.
He was in serious error concerning “the hope on which the whole Christian faith depends”. God does not inspire error.
It also means the Bible is in error too. It cannot therefore be the Word of God, though it may contain fragments of the original revelations.