"Also, isn't this supposed to be the last time the Doctor can regenerate?
Yep- though the advantadge of sci-fi, moreso for a time traveller, is good writing can easily fix that."

 

erm nope.

ppl have been getting that wrong. 12 Regenerations, 13 Incarnations.

 

Hartnell was Incarnation 1. the first Regeneration then brought Troughton, Incarnation 2..

I'm not sure where ppl started mixing up.. the Deadly Assassin set the final incarnation of the Master as the 13th body...

basically by these rules, the Doctor has 1 more regeneration left after Smith leaves...  12 to 13.

*tho the 50th may throw a spanner in that...