From a reputable member of the Doctor Who leak discord known as "SoldierBoy27"
"I hear that the 2026 Xmas special will act as a finale to this incarnation of the show, it's a huge celebration and feel like a bit of a blockbuster. However the show will not be ending completely and will return for a new series down the line - but whilst not a complete reboot the new series will be the closest thing we've ever had to a reboot since the show began in 1963. Expect a scaled back and somewhat more mature incarnation of the show. The BBCs strategy is to start small, build up a strong and stable audience again (particularly targeting young adult audiences and above) and slowly grow from there. Jack Thorne was in discussions to take over a few months ago, but no idea how far those discussions got"