I don't see the cut from 11 episodes (10 regular-Series episodes plus a Special) to 8 episodes being a permanent thing given that the only reason it happened for Series 13 is that it's going to take more time than usual to shoot each episode.
I also don't think we're getting a Special because it'd be very difficult to deliver a satisfactory narrative in just 7 episodes given the way that the franchise is currently structured.
I also don't think we're getting a Special because it'd be very difficult to deliver a satisfactory narrative in just 7 episodes given the way that the franchise is currently structured.