The beginning of December feels a little late for it to match the cinematic or home video releases of Iron Man 3. My personal inclination would be that this had to do with some kind of production dissatisfaction. Maybe they'll do well during the Christmas shopping season though. This pushback is a little disappointing (I was pretty curious to see how the first movie from MAS would be) but if it's to boost the quality, I can't be mad at that.
"I've had the same car since I was 19 years old, and never had a problem, yet this thing falls out of the sky every other Thursday." - Maria Hill