We know that he wants the job because he admitted having applied for it. I don't know why I dislike the idea of Snape's becoming the new DADA teacher so much. Probably because it feels like an exaggeration of the classic fanfic scenario with the Mysterious-Sword-Wielding-And-Curse-Breaking-Slim-Yet-Curvy new DADA teacher or the return of Lupin as DADA teacher. I think whoever gets the job should be an outsider and new to us, as usual. Did I mention I'm conservative?