If he were to regenerate maybe he will become a redhead finally. I saw someone mention Rupert Grint (ron weasley) in one of the Doctor Who facebook page. He was not bad in Harry Potter (which probably would elminate him for Doctor Who since he would be well known) movies, even though they make Ron more of a punch line then anything else.
I do like the idea of using an unknown (well not widely known) for doctor who.
So do we actually know that he is leaving during the christmas special or is he going to have some episodes in 2014? I will miss him so much. : )