Regarding the trailer being released on Christmas Day, my opinion is that this is no coincidence, and if you all remember, the Prometheus crew first entered the pyramid on Christmas Day.
Charlie Holloway: Captain, would you please tell the survey to suit up and meet us in the airlock.
Janek: There's only six hours left of daylight. Why don't you leave it till the morning.
Charlie Holloway: No, no, no. It's Christmas, captain, and I want to open my presents.
Coincidence? I think not!