I voted glen and rosita, but mainly because I hope it won't be Darryl (my gf couldn't handle that).
although they are setting up a conflict between rosita and Abraham and the other girl, whose name is escaping me, that may be too much with everything else next season, so I could see them nipping it off.
Darryl makes sense because he won't reconcile with Dwight and that limits the arc of the show. He's also running out of usefulness as a character devise.
Glen is obvious choice because of comic and he's the moral compass lately, never a good omen for a character in this show.
I'm surprised you didn't name Maggie as an option, not just because of the pregnancy pains, but also because I don't see how they bring another baby onboard. It would be just the sort of heart wrenching stuff this show lives for.
Speaking of, whatever happen to Judith?