Impossible Astronaut spoilers ahead:
What if it wasn't 11 that died in the beginning of the Impossible Astronaut? Someone mentioned in the gender-changing Timelord thread that when Romana regenerated she tried on several forms and deliberately settled on her final regenerated form.
The Doctor never appears to do this, but why? Someone suggested that the Doctor's regenerations were always unplanned and under extra stress. It's also possible that it's a skill he never mastered. Either of those cases could presumably be overcome. The Doctor can be fortunate to have some proper prep-time, or he can learn the necessary skill in the mean time.
Now, why am I suggesting this? Because it means the Doctor can regenerate into a different form for 12. 12 can have loads of his own adventures. 12 can then regenerate into 13 who looks just like 11 and then come back and die in Utah.
The Doctor never appears to do this, but why? Someone suggested that the Doctor's regenerations were always unplanned and under extra stress. It's also possible that it's a skill he never mastered. Either of those cases could presumably be overcome. The Doctor can be fortunate to have some proper prep-time, or he can learn the necessary skill in the mean time.
Now, why am I suggesting this? Because it means the Doctor can regenerate into a different form for 12. 12 can have loads of his own adventures. 12 can then regenerate into 13 who looks just like 11 and then come back and die in Utah.