Peter Capaldi announced on BBC Radio 2 that his will be the last season he will be the Doctor. As the 12th Doctor he received mixed reviews. You either loved him or hated him which in my opinion was not fair to him for those that hated him . Personally I think he did a great job as the 12th Doctor however I thought the writing was weak with the exception of a couple of episodes. And there was a different tone to the filming of most episodes which took a lot out of the flow of the series.
This actually came to no surprised to me considering Steven Moffat is stepping down and being replaced by Broadchurch creator Chris Chibnall. In the past that also meant a new Doctor.

See BBC UK Doctor Who Peter Capaldi announces he will stand down as Doctor Who at the end of the year

Peter Capaldi said:

“One of the greatest privileges of being Doctor Who is to see the world at its best. From our brilliant crew and creative team working for the best broadcaster on the planet, to the viewers and fans whose endless creativity, generosity and inclusiveness points to a brighter future ahead. I can’t thank everyone enough. It’s been cosmic.”