So there is talk that they have cast a 19 year old girl named Hannah Murray. I actually quite like her look and think she would be an excellent choice if they mean to go too young for romance...she could easily play 15 or so...and then they could have her be a Rose/10.5 granddaughter...or Jenny's daughter...which seems very likely to me given we are going to hit the 50th Anniversary soon.
I've just always felt they were going that way...give the Doctor some pseudo-family and "The Doctor's Daugher" and the biocompatible 10.5 make it likely. I could be completely wrong about that, of course. And, personally, I don't really want that to be the promised end to the Doctor/Rose love story. I mean, I wouldn't mind 10.5 providing genetic material but I don't want Rose to have lived that life. Still, I think it would go a long way toward giving Matt some street cred as the Doctor if he was someone's grandfather.
Here is a link to a picture of Hannah. http://www.exposay.com/celebrity-ph
She was in a show called Skins and she seems to have quality acting chops from that work. You can see her in action on YouTube. Some of the action is quite graphic, though.