When Cas took down Sam’s wall, the angel-god had promised he would ultimately save Sam from the trauma. But as Misha Collins told Zap2It, Cas will renege on that promise: “No, he wants Sam to suffer for a while. Sam's basically f***ed."
This will understandably not sit well with Dean. Collins said while there’s always hope that Cas and Dean’s relationship can be repaired, it will not be an easy fix, and any reconciliation will not occur in the first 2 episodes. There’s some question if it ever will, because it is unknown if Collins will return to the show after those 2 episodes.
Meanwhile, EP Sera Gamble said that Cas will be dealing with a lot of rage and resentment when we see him in Season 7, because of his unresolved quest to find God:
“Cas went looking for his father and his father never showed up for him. He's furious about that. He feels like everything that has come after for him has come after because he had to do everything. He's kind of like that latchkey kid who had to take care of the kids and take care of the kids and take care of the kids, because Dad never came home, so there is this sort of resentment. But if you're not God, you're not God. There's a reason God is God, we discover, over the course of this storyline."