There is no doubt in my mind that it is going to be Hagrid, and I'd be willing to bet a substantial amount of money on it.
Harry really doesn't need Hagrid anymore. Hagrid sort of introduced Harry to the entire wizarding world, but now that Harry is solidly a part of it...thematically, Hagrid is no longer necessary. Also, he is going to visit the giants right now: a very dangerous road to be taking, I guess.
Also, JKR said that this death was *very* hard to write - and she has said numerous times that Hagrid is one of her favorite characters.
And I seem to recall reading a transcript of an interview with Robbie Coltrane when he said he was not signed up for all seven HP movies.
I definitely think it'll be Hagrid who dies. :-/
--L