Looks like he might finally have had enough of the ming-mongs. 
http://women.timesonline.co.uk/tol/life_and_style/women/celebrity/article6228879.ece
"Russell T. Davies, the screenwriter who rebooted Doctor Who, is leaving Britain to pursue a career in Hollywood. Well, that’s the conclusion we drew after spotting the Welshman, who will quit the BBC series when David Tennant regenerates, patiently waiting in the work visa queue at the US Embassy yesterday. A spokesman for Davies invites us to “speculate away” about his trip. So we did."
Hmm... Following Julie Gardner to the BBC's LA-based offshoot to work on the "Doctor Who" movie?

http://women.timesonline.co.uk/tol/life_and_style/women/celebrity/article6228879.ece
"Russell T. Davies, the screenwriter who rebooted Doctor Who, is leaving Britain to pursue a career in Hollywood. Well, that’s the conclusion we drew after spotting the Welshman, who will quit the BBC series when David Tennant regenerates, patiently waiting in the work visa queue at the US Embassy yesterday. A spokesman for Davies invites us to “speculate away” about his trip. So we did."
Hmm... Following Julie Gardner to the BBC's LA-based offshoot to work on the "Doctor Who" movie?