Doubtful. If that were the case, you'd think that they'd either not confirm a release date at all and just let it be vague as to when it was coming out and what platform or simply wait a week to release the trailer.
I agree that if everything could be revealed by November 12th, then waiting could have been wiser. Still, it's hard for me to believe that Bethesda is going to release exclusive content for PC and PS3. I'm more inclined to believe that they underestimated how angry/shafted PS3/PC players would feel at the prospect of a new time-exclusive DLC.
Edit: going by Gstaff newest replies, yes, non-xbox players are getting dragonborn sooner than what a time exclusive would suggest (January 4th) so YAY! we'll be able to spend a happy Christmas with the new Skyrim content.