Foreman has said he was emotionally decimated by the Ali defeat & that it took him about a decade to actually get over it & put it in perspective.

Ali beats him in a rematch regardless because he was in Foreman's head. It might have been a decision or a stoppage, but whilst they were still both pros, I can't see Foreman winning, because he didn't get over the defeat & re-invent himself as a fighter till after Ali had been long retired.