As I said, I have heard nothing of the NFL moving their HQ. They may have stated that at some point. They aren't the press conference types like the NBA. You usually find out their news through articles and interviews or after meetings. Was there a Superbowl winning bid announcement from the NFL? Nope.
The NFL has quarterly "owners meetings". From studying articles, half seem to be in Dallas, no surprise they knew what hotels they would book. They seem to like Nashville and Washington as well. As I said before, they are not press release people, but usually you'll see it mentioned with some new rule or something. MLB seems to like Dallas for their winter meetings as well. I'm guessing these are very closed door sessions, which is why you see little mention of where and when this stuff is scheduled.