A marketing departments job is to sell the product and bring in the guests. It doesn't matter how they do it. You think this is bad? Seriously. Look at Kings Dominion and their Planet Snoopy announcement. This is what ALL marketing departments do. Hype hype hype. If they came out and said "Oh come and see the dull boring Fantasyland Expansion or not" I'd probably be selling my stock. Not to mention a bunch of people would be losing their jobs.
Well . . . a lot more marketing campaigns fizzle than you'd realize. Believability is part of the equation, if you make unbelievable claims and don't showcase the product, then you turn customers away, so a marketing campaign gone wrong is sometimes worse than no marketing at all.
The problem with Disney's ad is that you see nothing, zero, zip of the new Fantasyland. It is almost an attempt at a viral marketing type thing where you get potential customers whipped up into a frenzy all trying to figure out what this mystical new place is. Only, Disney's new ad is kinda confusing. And you don't want somebody looking at the mysterious map of FLE and then be disappointed with the real product. WDW isn't about tricking families into a once in a lifetime vacation, they're working hard to get the folks who come back every 3-5 years, look at all of the DVC units they've built.
I see what they are trying to do with the mystery angle, but given how photogenic most Disney parks are, most potential guests would want to see the "goods" before making reservations. Surely, we will see these commercials, and they will be much more effective than what they have put out.
Also . . . they've got a "Finding Fantasyland" website, but I would guess that most interested fans would know about boards like this one that have hundreds, if not thousands, of over-the-wall shots, behind the scenes videos, and commentary. Advertising is about knowing your target audience, not sure that they'd bring in any more interested parties with this.