In the comic book “Crisis On Infinite Earths,” Pariah was saved from Anti-Monitor by The Monitor, which may explain Nash Wells’ whole little speech.
While Pariah is more or less invulnerable and immortal, he’s physically powerless to the events that pass.
Admittedly, Nash Wells could become someone else in the mega crossover, but this theory seems to check a lot of boxes especially considering Pariah is confirmed to appear.
Although we can’t be certain, my guess is that Nash Wells will become Pariah.