Eirik beat me in suggesting James Newton Howard 🙂 . I think he – and Alan Silvestri – would be excellent choices.
With those two, there would be no need to actively try to emulate Williams – if they stick to their own, large-scale orchestral styles, it would mean we could still get meaty, skillfully orchestrated scores that would sound late-romantic, but still modern.
A lot of people seem to think Giacchino and Desplat would be natural choices, but I’m with others here that they would not be at the top of the wish-list. To my ears there’s something too straightforward and unimaginative about their orchestrations, especially when they write large blockbuster-type scores.