You seem convinced that Trump is going to be reelected, in that case a Democrat is 100% guaranteed to win in 2024, and they'll likely win a second term as well, so President Nikki Haley isn't happening until 2032 at the earliest.
No dems will only get 1 term if they win.
The Republican base is literally dying off, unless the Democrat who is elected in 2024 is a complete disaster they will win a second term based on demographics alone.
Republicans might change as the old white guys go and a newer and more diverse Republican party emerges, causing demographics to start meaning less. But yeah, I guess the Dem would win re-election but it is very early to think about 2028.