I think Trump will groom someone.

I agree, because I agree with the notion above that there is no bench. Trump knows there is no-one (that we're aware of) and will himself try to organise someone. Perhaps he is already doing that behind the scenes. Perhaps he will fail. But I'm sure he's aware of the need for a successor holding the same general ideals because without one everything he does achieve will be dismantled very quickly and all of his time and suffering will be wasted.