As we all know, Peter Capaldi has not signed onto Doctor Who past Season 10. We might also find another staple in the show leaving after the next season: Steven Moffat, the lead writer and producer on the show for the last 6 years.
In an interview with Radio Times he stated that although he is not sure when he will be leaving he is actively helping find his replacement. He states that the show is so important to him that finding a new successor is something is more than willing to help out with. And don’t hold your breath for Russel T. Davies to return because he won’t. He clearly has moved on as stated in Radio Times interview from last year, though Moffat does invite him back to write every year.
So Season 10 is the last guaranteed season with both Capaldi and Moffat. Right now the next big decision really surrounds who is going to play his next companion, as we saw Jenna Coleman exit the show at the seasons end. Capaldi has said he doesn’t want it to be a male, which I don’t think Moffat ever imagined. But Moffat said he and the other writers have an idea of how they will be introduced.
There is no official release date as of now, but a good guess would be early Fall, as has been the tradition in past years.