I keep hearing this in my head in regards to Sam. I speculate that he does not know where he has been or how he returned. I also speculate that Sam eventually got to Heaven before being sent back to Earth because his work on Earth was not yet complete. Will it be like Buffy season 6? Will he be confused?
According to spoilers, Sam is more pragmatic and cold this season. To me, that means he is more angelic. Perhaps being trapped with two angels influenced him.
Will he have powers? Hmmmm! I say he has them in him, but will he use them, I don't know. If he's up against monsters that are not demonic, his powers seem to not work. And from a witing point of view he can't over use them or that will hurt the story.
Since the two who wanted Sam and Dean as meatsuits are locked in a box somewhere, that means Sam and Dean are free again and no longer angelic pawns! That also means they are more vulnerable and it is possible for them to be killed and stay that way. I will be glad to see them have some autonomy and not be used.
What do I foresee:
Conflicted Dean with his love of Ben and Lisa
Early S6 Sam cold and emotionless
Same with Castiel
The monster world threatening the safety of Earth
The Campbell family history, how some were in deep cover and not found by Azazel
More teamwork fighting
More brotherly autonomy
Later reveals that Sam came back not quite the same
Dean's realization that once in the Family, you die in the Family
Heaven and Hell's power structure is disrupted, who will fix it?
Gabriel returns (he has too, Richard Speight is too awesome as the wild angel)
Raphael out to get Castiel and more (there is another angel, that we know as facts...he's rogue)
I foresee 7 total seasons. They could end it with Dean in Heaven and Sam in Hell to keep the balance! Just joking on that. No, I think they will just keep on fighting until the end.
I think what I love most about this card is that it represents temptation. I like that the artist chose to show that both Lucifer and Michael went about recruiting Sam and Dean to be vessels. I like that it shows the equality and parallel in both sets of brothers.