Ok so I just recently thought of this...
In the episode "The Name of The Doctor", you see that Trenzalore is to be his final resting place involving a large epic battle and you see his floating timeline energy inside The Tardis..
Here's a problem I was thinking about the episode where Smith regenerates into Capaldi.
How did the Timelords give The Doctor more regenerations without creating some sort of paradox or cause problems with timelines...
The Main reason I ask this is because Trenzalore is supposed to be The Doctor's final grave...
If Trenzalore was to be his final grave and giving him more regenerations changes this, doesn't this mean that The Name of The Doctor would have never happened?
And if that's truly the case that would mean that Clara never went inside his timeline to save him and therefore Clara would have never met The Doctor to begin with.
Also another thing to note is that if Trenzalore is still the final resting place of a future incarnation of The Doctor wouldn't that mean that Clara would have seen his future incarnations as well... if we assume that The Doctor has X amount of regenerations after turning into Capaldi, given that there is some debate as to if he used up some of his regenerations shooting down the Daleks in the last episode.
So all in all doesn't what they did completely mess up the chain of events that would have lead to him going to Trenzalore to begin with?
If I'm not being clear you can look at the Grandfather Paradox:
the time traveller went back in time to the time when his grandfather had not married yet. At that time, the time traveller kills his grandfather, and therefore, the time traveller is never born when he was meant to be. If he is never born, then he is unable to travel through time and kill his grandfather, which means he would be born, and so on.