Message #71030

[Exterminate]

You've pretty much summed up what there is to know, to be honest. With the exception of the part where the regen limit died with the Time Lords. That bit is just fan speculation. More often than not these stories changed the details to suit themselves and there is a lot of fan debate about it.

The Ace thing can be discounted from canon because although you are right and it was planned, it never happened so it's not strictly 'canon'. The reasoning behind Rivers regens is ropey at best and probably worth ignoring for its silliness. If making Time Lords was that easy, why not just kick start the race by getting jiggy mid flight? Although, it does sort of help in the argument of whether or not Time Lords and Gallifreyans are one and the same. The reason she can regenerate is because she was conceived in the Time Vortex and so ended up with Time Lord DNA. An improbably story, but if Time Lords were an order and not a race, they wouldn't have their own DNA. My personal opinion though has always been that they are one and the same.

The stuff with SJA I think was meant as a joke. Perhaps not the fact that he can do it more than 12, but I think 507 was just a number plucked out of thin air and the Doctor pulling Clyde's leg, somewhat.

As for the stuff in The Brain Of Morbius, this is something that was more implied than stated, and so I, along with most others, choose to ignore it.

As we get closer to that 12th regeneration and beyond, I would expect it to get even more muddied. They obviously, as long as the show is still a success, will want to continue it and so will find a way around it, which is likely to contradict what we know already. On the other hand, the number of regens hasn't been addressed in NuWho so there is nothing to say they won't just ignore it completely and carry on.