Really? I honestly don't think that will be the case. You need to take everything in to account here. People work on Boxing Day in England, so they will massively sabotage their ratings if they decide to put on the Tenth Doctor's finale on Boxing Day.
If they do anything, it'll either be Christmas Eve for the first part (people work on Christmas Eve too, but the first part can be caught up before the finale), and the second part on Christmas Day. Failing that, they'll be shown on Christmas Day and New Years Eve/Day.
Also, if people want to take pot shots on when the Waters of Mars will be released, look at what BBC currently has on right now. The Formula One will be finished next weekend, so throughout November there will be no more set-backs. Then you've got the current shows that are on TV right now that conflict with the timeslot Doctor Who usually rests on (between 6-8pm). Merlin has 8 more weeks to run, and Strictly Come Dancing has 6 (so, if they were letting both shows run their course, the earliest would be December 6th).
The BBC won't show Doctor Who on BBC Two as it'll conflict with their other shows. So one of two things are going to happen - they'll leave one show off the air for a week (which will be Merlin, they won't take Strictly off), or they delay Doctor Who til December 6th.
Personally, as Waters of Mars looks to be a "scary" episode, I've got an odd gut feeling (that's more of a hope than anything else), that Waters of Mars will be shown on October 31st (Halloween), which means it'll be shown just a day after his depature on SJA.