Many people refuse to believe that Timelords only have 12 regenerations, thus meaning 13 bodies.
Most people think that we are on the 10th Doctor at the minute and that was true until the last episode of season 4. The Doctor did techniquely regenerate but finished the process by transferring the rest of the energy into his old hand. This means that David Tennant is actually the 10th/11th doctor. This means he only has 2 more regenerations left, as we know - after the specials in 2009 David will be leaving and Matt Smith will be replacing him, this means the 12th doctor will be from 2010 onwards. This leaves only 1 regeneration left for the doctor.
I can't remember the link right now that proves the 12 regenerations but a reference to it is made in the most recent Christmas episode. I can say without ruining it that the current doctor asks the Doctor from the trailer (not ruining story) whether he's the next or the next doctor. Only saying it twice.
I know this isn't much proof as I can't remember the quite exactly but those of you who have watched it will know what I mean. I will try and find my source proving the 12 regenerations again so I can prove it properly.
I would like to know peoples opinions on this matter. What do you think they will do to continue Doctor Who after he runs out of regenerations.
UPDATE: I havn't found the website I found it on but I have even better, in a episode of Doctor Who itself. You will find it in the Doctor Who (1963) page. Season 20. In 'Mawdryn Undead' Peter Davidson says that he has 12 regenerations and has already used 4. ( Peter Davidson was 5th body of the Doctor of course)