I'm not sure you quite got my point... if theres no project, its still free advertising. Jurassic park 4 had nothing done for years, and arguable still does not. They know they are making a new season, delays are normal, why wait to announce it? especially when they actually had an audience for the 20th anniversary event?
That's actually really smart from a business standpoint. But eventually - say we go 9 more months with no updates - someone official would have to speak out to keep the interest up.
To avoid looking foolish, companies try not to give updates until they have something solid. For example, officially announcing a delay ( assuming there is one ) when they do not know how long the delay will be would be a not so great idea. Until now its still summer of 2013, but once they work out whatever problems they are ( supposedly ) having they will let us know the new date.
But then they'd just say, "Hey, we're making a new anime. More information coming soon!" and not, "Hey, we're making a new anime and it will be out next summer."
That doesn't make any sense at all. Announcing when the project will (theoretically) be released is important as it builds anticipation up to that release. If its part of the initial announcement it sticks to your mind. if they just say "they are making a new sailor moon show" and theres no date attached, no one knows when to expect it.