Hickman is more of a team-books guy than a solo hero writer. That extends to his independent work too. So it's unlikely to be him.
Jason Aaron might be a possibility but he's got independent stuff and others and he's probably reached the "Move to DC" age or near-abouts. Has Marvel announced what he's doing next after King Thor wraps up?
Coates is plausible but he's got a budding literary career and other stuff to tempt him away. Cates is best placed of the lot to make the move.
Exactly.Another possibility is that it's someone who hasn't exploded in popularity yet. Maybe a Dawn of X will do for one of those writers what Venom did for Donny Cates, or what being on the Brand New Day team did for Dan Slott, which will put them in a position where they can be seen as a plausible Amazing Spider-Man writer.
Grant Morrison didn't exactly leave Marvel happily and he hasn't worked at Marvel after New X-Men wrapped up. Scott Snyder seems more plausible than King does of the two.The final category would be someone who isn't currently working for Marvel, either one of DC's top writers (Tom King, Scott Snyder, Grant Morrison) or someone outside the big two.