Of course, there will be a GOP president after Trump because they will just cheat. I fully expect Republicans will just go full blown undemocratic.
See, these are the types of posts we DIDN'T used to have on Atlas ... pre-2012 Atlas looks more and more like a golden age each passing day.
I think Trump will be the last Trumpian GOP President ever, because demographics make it harder and harder with each passing year for someone who is vocally anti-immigration to be elected.
... Now as to the OP, obviously Trump won't be the last Republican; the more interesting question is what form the GOP takes in the future. It could be a Trumpist form, a return to Buckley-style movement conservatism, or maybe a yet-to-be-revealed third form. The middle option of those is the least likely IMO.As for what the GOP base will be focused on in, say 60-70 years ... I am not sure. However, I will bet the beach house that the next successful GOP "realignment" will be exactly what the folks currently what Trump hate, haha: a rather measured, Burkean conservative response to a Democratic Party that had a bit too much power and overplayed its hand. Eisenhower-esque.