C.C. is a character only second to Lelouch himself, and moreover her fate has been tied to Lelouch's for the duration of the whole show, so I deem any prediction involving Lelouch but not C.C. has a fundamental flaw. It would be quite an unstylish ending. Well, it's not like an unstylish ending couldn't happen but I certainly don't hope for one.

The only way I can immediately see Lelouch dying now and C.C. trudging on is if she becomes some sort of a story teller (she did the narration already, alright) and a kind of character who will "make sure the mistakes of the past aren't repeated". But I can't really see Lelouch dying now suddenly and C.C. left standing on nothing, as if the script writers would have forgotten such a character existed.