Problem: Critics note that Paul says that “we” will remain until Jesus returns. From this statement, they conclude that Paul made a mistake, thinking that Jesus would return before he died.
Solution: This could refer to an editorial or royal “we.” For example, in the past tense, a history teacher might say, “We took the beach of Normandy in World War II.” When they say this, they are in no way implying that they fought in this war; instead, they are claiming that the Americans took this beach. In the future tense, an environmentalist might say, “When we destroy the ozone layer, we will perish.” By this, the environmentalist is not claiming for certain that he will be alive at this time, but humanity will be alive. If Paul believed that he would certainly be alive at Jesus’ Second Coming, then he wouldn’t have said we; he would have said, “I will be alive and remain until the coming of the Lord.”
The writers of the NT probably believed in the imminent return of Christ, because all of the necessary conditions were in place (e.g. Israel was a nation, the Temple was still standing, Rome was in control, etc.). Once these signs were displaced (e.g. Israel was dispersed, the Temple was destroyed, etc.), they probably came to realize that Jesus wouldn’t come back for some time.
“For this we say unto you by the word of the Lord, that we which are alive and remain unto the coming of the Lord shall not prevent them which are asleep. (1 Thess 4:15)”