Trump is old and is not the leading example of a healthy person. I think there's an entirely reasonable chance that nature takes care of this one for us.
That said, I don't think it matters at all. This isn't a Trump problem. Sure, he's the figurehead, but there are ample figureheads waiting in the wings, just as malleable to the alt-reich's needs. They will be more than happy to step in and allow the current dismantling of the USA to continue, and for Something Very Else to be built in its place.