Easy one to answer Skippy...it'll be BA when they buy Flybe, and send a dozen triples up north
Apart from that remote possibility there is no other true hub airline for MAN I'd say, and even the BA operation I can see as workable is a "base" really not a "hub".
Despite me seeing reasons why my stupid ideas could work, we do know BA/AA/IAG are sitting up, taking note and possibly making plans themselves ex MAN. My heart says that could be a BA base, my head says it will be with other OW airlines again serving their hubs and expanding that way to fight off the likes of DL/VS.
One of the first things to happen at MAN with any new development with be to make it possible to travel from T2 to T1 to T3 airside, which can only help connecting passengers.