I think sam is still in hell, and this will be the final supernatural season.
It will end with Dean killing sam - in a micheal vs lucifier style battle.
Look at Kripke's ending - and tell me you cant see Dean crying while killing Sam.
I believe the entire story is leading up to that point. Both Tragic and Beautiful - how the best stories are told.
Either that or when it comes to the point of dean killing sam - the good 'ol boys will turn and defeat evil in their own unwritten way, using their classic misdirection.
Either Sam dies or they defeat evil. Its the only way I see supernatural ending.