Oops.
Disney+ have accidentally confirmed that the Christmas Special will indeeed be on Christmas Day. Oh, and they threw in the title too. Which is exactly what the leaked synopsis from months ago said it would be. So add that to the other bits we know were right and it's safe to assume the whole thing is correct.
If anyone could break the BBC's maniacal and insane secrecy over broadcast dates, it would be Disney. People with BBC America complained about how they couldn't market Doctor Who because the BBC just had to keep its broadcast dates secret until the last possible moment. (Truly. I was in several of those conversations.) It doesn't make any sense when your partners are commercial broadcasters who have marketing schedules. The BBC's secrecy ran headlong into Disney's marketing, and it's the BBC's blood all over the highway. It's twenty-fucking-twenty-three. It's long overdue.