Most likely they are pulling in extra support to get the game finished. They work to a tight deadline and release date, it's not like they are going to push the date they have chosen back. In the past the Developer would probably have just been allowed to let the launch slip back, but since it's so important, Activision will just throw money at it to get it finished in time. It's very similar to how things work in the film industry.
I think it would be silly to think that Black Ops 2 won't be one of the biggest, if not THE biggest selling game of the year. I think people certainly realise its getting a little stale now and MW3 was a let down in a number of ways. I'll still buy it, even though I'm not some COD Kiddie who will play it for months. Black Ops turned out to be one of the better COD titles, so it will be good to see how they follow it up.