The Wormhole wrote:
As I've said before, I believe as long as Moffat is running the show, River will always be back. And even after he steps down, if he stays around to contribute an episode a year, the possibility for River's return still exists.
As for Vastra and her gang, I'm pretty sure they'll be back. At the very least, having Jenny killed and resurrected implies there are plans to revisit the characters, otherwise they could have just left her dead. In fact, I can see them easily making an appearance in one of Capaldi's first few episodes. Sort of one of those "and now here's something familiar after all the changes we've thrown at you" type things.
Yeah, unfortunately, I don't think they're going away anytime soon. They'll probably be what the UNIT family were to the third and fourth doctors transition. Moffat did say Capaldi's beginning would be a bit like T Bakers first few episodes, so maybe the detective trio will be what UNIT were to the fourth doctor in robot.
Sadly though. Strax has ruined the Sontarans, and the very young viewers will only know Strax and not the other Sontarans stories, so to them, eventually if evil somtrans ever come back, it'll be weird to them.