I think the 2013 shoot blocks have been agreed upon in prinicple already, since they apparently have plans on everything they need to do leading up to the anniversary in November. Assuming they want to do something DW for Christmas next year, they'll have to do it around the same time in the summer as usual, so it'll be pretty solid already. Moffatt will be glad to have a little extra time to polish his Sherlock scripts, but I'm sure he'll be just as hands-off during filming as he has been on his two shows so far.
Mark