well, by dead i mean not in hell or purgatory. In heaven, I guess.
A good end.

But with the way Dean disappeared, I think assuming he was okay was a bit too wild from Sam, sorry.
And he may not have Bobby or Cas, but he knows how to find a demon, how to contact Crowley (helloooo Sam),etc. He shoudl have resources to find out if Dean was dead or somehwere else.

I have one scenario, that I dobt very much they're going to take, that would fix this mess. For me, of course lol. I'm assuming they're hiding something from us, something important.

Sam did some sort of deal with Crowley. Crowley accepted (because, don't know, maybe he wants Sam out of the map, or because he's afraid Sam can bring Lucifer back, whatever) to help save Dean, and his 'help' is that monster boy that Dean finds in P. What Crowley asked from Sam was to stay away from hunting and his plans for a whole year, while he takes over the world.

or some crap like that. Something other than Sam is okay with not knowing what happened to his brother.