There are an awful lot of articles saying rumors that Tennant is leaving Doctor Who after Season 3/29 aren't true but until today I hadn't seen any mention of new casting. Rumors are what they are so I take it cum grano salis that Jason Statham (imdb) is next up as the Doctor.
Probably not worth commenting on a rumor so unlikely, Statham's film career may not have been boosted by Crank but I find it hard to believe he's looking for series tv work, yet I can't help but wonder what he'd do with the role. He was brilliant in Lock, Stock , Snatch, and proved he is a legit action star in The Transporter. But, while the Doctor is supposed to be a master of Venusian karate, action is hardly the show's calling card. I'd imagine he'd have to play the role more Turkish than Frank Martin, which wouldn't be a bad thing.
Still, I hope Tennant sticks around a few more seasons. The Doctor doesn't have enough regenerations for the role to be revolving door.