I don't think Ubisoft hurt this year in earnings, so perhaps this move was more of a business choice so that they can be sure 2014 will look good on their earning reports.
I think the delay has more to do with the fact that Ubisoft didn't want to release both their tent pole franchises during the same time period...I think they would have preferred pushing AC4 back but since that has more of a built-in fan base plus a new AC game always comes out in October/November they made the decision to delay Watch Dogs