From what I know about Sam's girlfriend it seems like you're partially right. But I still think she'll stick around for a bit in one way or another.
As for Dean's purgatory friend, I think that might just be the same character as the kind-of-bad-guy spoiler we had a while ago.

With Crowley and Kevin both being a major part of the storyline I don't see how they can possibly not include the angels as well.