Honestly, I think it will be someone no one's ever heard of. Because he's a known nutter now, so the only person who would be with him is someone who wants the fame very badly and can't get it themselves. It'll be an actress/model who is really making her living as a waitress, or the assistant makeup artist on his next movie...
I don't know. I think it has to be an actress, and one with also questionable abilities so that you think for a second that tom has some credibility.
Nicole? Eh, she did a couple good films but she's no gold standard.
Katie? I direct you to Pieces of April, a great indie film, and ask was it good acting or just a great part for her? I rather like Katie because of that role.
My guess is that chick from the twilight films..