There's no way they'll kill off Tyrion. I know GOT has a rep for killing off anybody but it seems clear that GRRM has some favourite characters (Tyrion, Arya, Danaerys) that I expect to be around until the very end (or at least close to it). It's a shame though that whatever will happen to Tyrion it's doubtful will ever get to see him with power and involved in King's Landing politics again, which is when he is best.