I would be surprised if it's anyone but her. Brother. Oh well, I'll enjoy the good snarking times she'll provide, and I don't think the media will go so easy on her this time. Especially since she originally said she had no interest in show business and just wanted to go back and teach. That, and her interviewing skills.
I wouldn't be surprised if they wait until the premiere to announce the co-host to keep everyone in suspense (or try to) but I figured we'd get the big announcement during TB finale. It's bad enough they have to announce the cast during that show. Maybe I'll get lucky and because Melissa is a former contestant on that show that's all it's about.