Press embargoed spoilers from the last episode of the finale:
The Doctor meets up with Susan eventually right near the end.
Conrad, who everyone thought was dead shoots her with a lazer gun just as she is going in for a hug with her grandfather.
He smiles, there is a close up on his mouth and a gold tooth that glints briefly before he chuckles and runs off.
Susan is dying in the Doctors arms.
He cries.
Belinda reminds him he still has some regeneration energy left, as seen in Lux.
Doctor says if he does that he won't be able to bi-regenerate any more, but it is worth it to save his granddaughter.
He gives Susan some regeneration energy and she regenerates into the actress Chloe Annette.
The Master bi-regenerares from Conrad, he is Russel Tovey, now.
At the start of the credits it says "The Whoiniverse will return in UNIT: The War Between Land and Sea."
After the credits there is a short scene where the Doctor asks Susan what she is doing for Christmas then the caption comes up "The Doctor and Susan will return in Christmas With a Penguin.