Honestly, even if Sam knew what awaited him, what would happen to Dean, it wouldn't change anything. He wouldn't take back the forgiveness he'd granted Dean because of something that wasn't in his brothers control, and Dean would never have chosen to become what he became. If Dean came clean now and told him everything that would come to pass Sam would still never be able to kill his own brother, even if it was for the greater good. Dean was actually in more danger of losing Sam by keeping this from him than he ever would be because he was a demon.
Sam took another sip of his own beer then nodded, looking a little dejected. It was true that Castiel's power was severely diminished with his stolen grace, but then a thought occurred to him. "I guess, but there's always the chance that if the portal picks him up that it'll bring him from another point in our reality, one where his mojo is in tact. I mean, it's a long shot and it's still technically waiting around instead of actively trying to get out of here but it's better than nothing." Sam wasn't sure whether he was trying to convince Dean or himself with the pretty feeble pep talk. He sighed and picked up a cue, mirroring his brothers action. He had to pin what little hope there was on Cass showing up, because he wouldn't even consider Crowley as an alternative.
Sam was surprised to hear that Dean was staying with Jo, knowing how he would feel being constantly reminded of what happened, not that he didn't want to see her he just thought it might be a little bit of overkill to actually live with her. He was less surprised to hear that he clearly spent the majority of his time at the bar than actually at her apartment. "You know you're supposed to make that money last a little longer than a week, right? You can't just go on a bender and then start hustling pool, not if we're really stuck here." He smirked a little at Dean and shook his head.