A lot of developers are cutting down on previews for many reasons (affects budget, production, time better spent on making the game), I know this because I see it at work. Dealing with previews takes serious time away from actually working on the game .. hell I can even give you an example of how this week has turned useless to me since I have to make marketing posters to be placed around EA (waste of time)
Marketing will really ramp up about 6 months before release, that's when it makes the most sense. since the game will be pretty much done by then, on a project that lasts several years its important to spend the very last one really focused in the game itself. Square just giving little bits and pieces every now and then works the best since they give you little bites and people can just be left with their own theories of what the game can become.