I really don't see any sound logical reason for Hamilton wishing to join Ferrari or Mercedes, although it would be interesting to see what Lewis could do with the Merc, much better than the current pair I'll bet.
Would Vettel or Alonso want Hamilton as teammate? Don't think so. And I suspect they both would have a say in it. And I really can't see why Mercedes would want Hamilton over Rosberg, they are Germans and do not rate Hamilton as high as Brittish people in general. And if schumacher leave, I suspect they would want a young di Resta etc. What other team could Hamilton go to with a remote chance of winning? Williams, Renault? FI? McLaren should be a no brainer for him. So I dont understand why he isn't signing asap.. Could it be that it is McLaren that are waiting ? Maybe THEY want to hold their options open? I think Hamilton would be their best option as well.