Lots of rumour flying around regarding the longevity of the Thirteenth Doctor. It was reported in the media some time ago that JW was quitting after this next, shortened series. Whilst never confirmed, it was noted that the BBC failed to deny either.
The other day the cover of the 2022 annual was revealed, and it doesn't have the Doctor on it. Just an image of the TARDIS. This has led some to speculate that we might have a new Doctor this side of Christmas.
Latest is that JW will see out this next series, and then there will be a couple of specials only in 2022, the last of which will see her regenerate.
Regarding the next series, there's a rumour that Donna Noble will cameo, and may actually be a relative of John Bishop's character. Monsters known to be featuring, because photographed in public areas, include Sontarans (with new silver and black costumes), Weeping Angels and Daleks. A word of caution about some of these is that scenes might not be filmed for the series itself, but for some spin-off project. Just look at all the filming that has gone into the Time Fracture experience.