It has nothing to do with exclusives, it is development times -
Gstaff: Bethblog. The Xbox 360 got Dragonborn first, but as we’ve posted, it’s our intention to get it to everyone as soon as we can. Developing the content takes a significant amount of time and effort for each platform, but we think the wait will be worth it. And as I noted in the post, that’s not it. You’ll be hearing more next year.