When he and Rick were on the radio for the last time and Glenn called Rick "dumbass" , just like when Glenn radioed Rick in the tank in season 1 episode 1(?) . I think it was a foreshadowing "goodbye" ... If he is gone, this is the first death to the group to "get to me" in awhile. Glenn and Carol have been my favorites for a few seasons now but I do agree it's nice to get new faces . Watching him (possible) be torn apart was rough.
Rick, Carl, Carol, and Michonne seem to the untouchables. Maybe Morgan too but I think the next important character that might go is Sasha or Abraham.