I don't really see how it can be viewed as off..
If you had multiple products you were wanting to get the most profit out of, would you put them out one at a time so that it was the "new and popular" thing at the moment, or would you release all of them at once and hope that they all got bought?
AC doesn't do as well in NA and EU, so it would make complete sense to hold the date and information on it until there aren't any other planned games to be released. Then they release information, get hype up, and the game well sell well.