The next election will be very interesting.
If trump is still functional (in the goes to rallies for a successor sense), will there be someone he can or will transfer his popularity to. I kind of doubt it. Anyone able to take on that popularity is a threat to him. Maybe he would do it for one of his kids, because he might think he could control them, but I still doubt it. So he might submarine his own party.

That would open the door for another boring centrist from the democrats that “plays ball” with the party elites.

If trump is too feeble to do any rallies and such. That would allow a trump like replacement to pick up the republican torch. This would push the dems toward needing a progressive trump like populist to try to win. The dem “party” (the people behind the scenes) would fight that. Just like they did when Bernie was up against Hillary. And could end up handing it to the new trump like person. This would be the path to your future one party system.

The third scenario would have trump die in office somehow. Vance would “play ball” with the rep party elite in a heartbeat. And he is more like a pre-trump politician. We saw that in the vp debate. But the party elite would probably back him. It could end up with the return of the pre trump days with boring poloticians who just do what the party elite say, with the party elite m9ving back into the shadows.