Apparently it's being confirmed that Season Seven will air in its entirety in the fall of 2012. There won't be a mid-season break (or if there is it'll be a short one), and the entire series will be shown in the general September-October-November timeframe, then the Christmas episode as usual. No word on whether this will continue after that point, but I imagine there's a good chance it will, and that Doctor Who is becoming a fall show instead of a spring show. (Recalibrating it to spring again after that point would require taking a whole year off, I'd imagine, due to shooting schedules and such.)

It's speculated that this is in part because Moffat is working on new Sherlock episodes that are coming out in the spring and doesn't have time for new Doctor Who until after that's finished. It's also speculated that BBC is thinking this might help with ratings since more people generally watch tv in the fall and winter when it's getting darker out.

I'm fine with whenever they want to show it. It will be tough waiting a whole year for new Doctor Who, but if this current season had ended in the spring as usual we would be waiting a year anyway. So whatever works for them, as long as it's good I'll still be watching.