Spoiler done short: Billie Piper was seen on set of S5 filming.
Seriously?!?!?!? Billie Piper is pretty much the only thing Who-related that would make me watch Moff's Who. Why?!?!? I'm hoping so very, very, very much that she is just visiting Matt Smith or something, because Rose involved with this version of Who just can't be anything but a million times wrong. Moffat writes her horrifically out of character, hates Doctor and Rose, and will likely destroy any lasting memory of their love story as well as the happy fuzzies those of us who do have for Rose/Ten II.
Why, Billie, why?!?!? PRETTY PLEASE BE HER JUST VISITING THE SET!!!!!!!!!