Americans' attention spans aren't the greatest, but in my view if he does end up running in 2024 I just don't see anybody else being able to win the republican nomination over him. His base is that mindlessly rabid. Does anybody really think Mitt Romney is going to get ahead of him for example or Ted Cruz, Marco Rubio, Tucker Carlson? Plus baring being forced like going to prison or something to that level he's not going to just give up the spotlight.
The greatest chance of something taking him down is if somebody is smart enough to keep pushing Big Macs his way so he keeps shoving his face full of them and suffers a heart attack in the next couple of years. I would say his further mental deterioration would normally keep him out in any normal circumstance, but he's unhinged and already has clinical mental problems as it is and too many people just don't care. Unless he's gets to a point he's not really functional anymore too many of his followers won't care. Hell, his stupidity is a common link for both of them. It's part of what binds them together, and they might actually see it as a positive.