Not even being a dickhead here, but running polls about two men who will be in their late 70's/early 80's in three years time seems quite presumptive 
I think Trump will manage to be Trump at least until the next election.
It probably depends on how well the Republicans do next year. If they win the midterms he will claim credit and drive that MAGA-A train all the way to the White House.
If they lose he will call them a bunch of losers, RINO's and pass the torch to Trump Jr. because the elections are rigged anyway.
Biden is probably not getting better but I also can't see him get any worse than he already is (if he gets any worse, than he has a serious condition and is unfit to lead anyway).
Right now, he's just old, confused and tired. Maybe he'll do an LBJ, announce he will finish his term but is not running for re-election as to 'clean' his slate for matters at hand.
That would give the Democrats a second chance to pick a better candidate. But rumors are going around that Biden is worried Kamala doesn't have what it takes to defeat Trump and thus he feels compelled to run if Trump does.
Biden like Trump seems unfazed by all the criticism.
Remember his position has always been "Just vote for the other guy if you don't like me".
He still has 2 - 3 years to steer this ship around, which is needed literally at this point.
