1. Limit? What Limit?
The least satisfying, but probably most likely, way of getting around the limit is to pretend it doesn't exist and never has. Holmes made it up as a throwaway line in the episode, and there's no real reason it should remain an accepted part of canon, or so the feeling goes among some. So...just ignore it. Pretend there's no limit to the number of times a Time Lord can regenerate. Sure, it's a lazy way out, and contradicts the whole point of the Master past his "beef jerky in a cloak" version, but it is very simple and doesn't really require much effort. I doubt that it's something Moffat would do (in his case there'd be a gigantic story arc involving River Song, Amy, Clara, some obscure Second Doctor villain and the Doctor's latest fashion accessory), but I suspect by the time Capaldi goes, we'll have a new showrunner, and who can say what she or he will want to do? Either way, this is a lot of questioning to no real purpose. Those who are worried that somehow the Capaldi Doctor, or the one after him, will be the last can stop worrying. As long as the show remains popular, the BBC will find a way.