My thoughts are yes the regeneration limit isn't important and COULD be dealt with by a throw away line but it is a potential storyline in it's own right, the doctor should permanently die but manages to avoid it to live forever?
The reasons I think they are going to tackle the regen limit in the 50th is these
1 it is a good point in the doctors story to deal with it
2. the regen limit has been discussed more and more on the bbc recently, It was discussed on BBC news on a bbc blog
http://www.bbc.co.uk/news/blogs-maga...nitor-23573730
and Neil Gaiman discusses it here
http://doctorwhotv.co.uk/gaiman-talk...imit-52305.htm
Al this in the past week, my feelings are the BBC is preaping the ground with all this so the talk of a regeneration limit doesn't come as a surprise to non hard core fans who might think it has just been made up for the 50th.
3. The introduction of Hurt as an assumed 9th Body of the doctor makes Matt Smith the final incarnation as far as I see it.
Let me explain I see each new time lord having being given 12 regenerations almost like a pill (or a seed as the last poster said) every regen uses up one of these regenerations/ pills. I am of the opinion (I know not everyone is but just my opinion) that Tenant used up a regeneration in stolen earth, he might have syphoned off a lot of the energy after it repaired him but he still used one of his 12 regens to carry out the repairs to his body he doesn't get that repair for free.
So if that is a regen (just my opinion) and hurt is the 9th incarnation of his body then Matt is the final doctor.
4. Also Trenzalore is the Doctor's grave and It gives the impression that it is Matt's doctor who dies there, no regeneration the doctor dies and becomes a stream in the Tardis. Clara seen no other doctors in the time stream so to me Matt's incarnation is the final one. Yes there are other ways he could die (shot during a regeneration) but it fits with the theory that Matt is the last incarnation and that is why when he dies at Trenzolore he doesn't regenerate.
This to me is the story of the 50th, avoiding the Doctors final death by getting him new regenerations. Maybe that's why capaldi was doing Hartnells signature lapel move
It's a theory and I appreciate there are holes in it but what is being a doctor who fan if you can't speculate nonsense