Hammo wouldn't work in Red Bull and even with Webber talking as though he doesn't want to be an RBR any more (he has to be ready to retire soon), they won't take Hammo because of how badly paired he was with Alonso. He gets on with Button, but that is because he knows give it a couple of years and Button will hang up his gloves too. To be honest he knows he'd be mad to leave McLaren as they are his team, much like RBR are Vettel's team.
Hammo is in one of the 3 teams likely to ever win the WDC/WCC, so if he can't get a seat at RBR, McLaren or Ferrari he has to start on the decent to back of the grid. He'll never do that. RBR have too many drivers waiting in the wings for a seat and Ferrari will never take him with Alonso there. It is never going to happen.