The Republicans will probably learn from their mistakes (arguably having a President wasn't a mistake but the kind they got was) and their successes (it seems that they didn't poison their own chalice enough to (yet) lose the other parts of government, but it's hard to credit Trump to this fact without assuming N. E. Other in the position would not - save for the old "look over here!" distraction he caused perhaps).
What have the Democrats learnt, though? Except that, whatever you think about the candidates, they managed to pick ones barely more popular than what the Republicans put up (and not enough so, in at least one of those cases).
It'll be a toss-up, at this premature stage, whether an unseated Trump goes on to become POTUS#47 (or #48, give or take the possibility of Harris bagging the next slot on), because of the total unpredictability of the next four years of US and world politics. I don't think mainstream Rs would normally back him but there'd be a non-zero groundswell of Trump-over-Relublican supporters who might be able to help him (inside or outside the Republican ticket). In a 'worst case'[1] scenario, that'd be a possibility.
[1] Depends upon your POV and the outcome. If the Trump-Party ticket falls behind the main parties' tickets, it might be quite ood for them.. but probably better for Ds.