I think what's gonna happen is sort of easy to predict. Apart from Bill, the episode we got focused highly on Missy trying to be good although there is almost a physiological barrier that hinders her from being as such.

After the latest Cyberman invasion is dealt with, Missy will break down, saying it's impossible for her to be good due to her nature.... (#s due to the drums in her head. She realizes she needs a complete reconfiguration of her genes, so Doctor takes her to the Chameleon Arch. Maybe due to the process, or because of the Cybermen, she regenerates into Professor Yana.)

Master, watching all these from afar, (#s perhaps can weigh in on the issue of how Gallifrey and him escaped the pocket dimension - a crucial information that Missy ultimately wasn't able to give, because she have not even been aware of the Time War. The coordinates of Gallifrey, an information Missy DID give to Doctor which was later falsified, was still true to her at some point, and she never intended to lie.)