According to UK Screen Alliance, Doctor Who Series 11 will have Christmas special.
In an article about Gorilla Group, a Cardiff-based post-production company which does online and finishing for the new Doctor Who series, UK Screen Alliance stated:
“The new series will have 10 episodes and a Christmas special.”
The ten episodes of the series will run on Sundays from October 7 to December 9. Because the eleventh episode is referred to in the article as a Christmas special, not a holiday or New Year’s special, it can be assumed the Doctor Who Christmas special will air on December 25.