At the end of LotTL, when the Doctor was talking about how he'd be looking after the Master because he was his responsibility, I found myself wondering if they were going to have the Master be a companion (albeit a reluctant one) for part of the third season. When I had that thought, I actually wanted it to happen, to see Tennant and Simm together as the last Time Lords journeying around for a while. It would have been cool.
Don't imagine that's what they have in mind for his new companion, though.
[EDIT- Just read the press release, and yeah- guess I was as wrong as I thought. Dang- I didn't really mind Tate, but to choose her as the regular season long companion over Freema? What are they smoking?]