I read that the plan was for Joe to get involved in Balor's match with Crews and start a longer term feud with Balor. Its all rumors anyway, but I still think Ambrose is more likely for the US title. NXT needs Joe more than Raw does.
There was so much noise about Bryan being the possible partner for Reigns and Ambrose at the last PPV, maybe they let it die down a bit so his return would be a bigger surprise? Would definitely like to see him come back.
At this point, Ambrose's name has been thrown around so much I would be disappointed if it's him. Especially after his last US title run. Same with Ziggler.