Edit: As I mentioned originally, I hadn’t watched much of Doctor Who. I had no idea the show progresses via season arcs, and each episode looked mostly detached from others in terms of continuity. In that same vein I thought the movies (i.e. specials) shared lore and notions from the show so far, but not necessarily be part of the continuing story. So yes, I was watching out of order. I’ve since watched everything, and am pretty glad I started where I did. Had I started pre-Moffat, I’m pretty sure I would’ve abandoned it.
I haven’t watched much of Doctor Who, and my question pertains to episodes I’ve watched a while back, so this may be just me misunderstanding or misremembering, as opposed to a plot hole.
In The Time of the Doctor, the 11th Doctor regenerates into the 12th Doctor. However, in The Impossible Astronaut, the 11th was killed. Yes, it was a future version of himself, but he still looked like the 11th Doctor.
Killing a much older version of the Doctor (and him travelling through time and all) is an effective way to not have to worry much about the event when writing the show, but shouldn’t that have made any regenerations into future Doctors (the 12th) impossible, since he died in his form as the 11th?