Oh, I feel it! It's in the air!
I think they probably also understand part of the challenge with this being the first 3D Zelda that is a direct sequel, that with what they've shown so far, they probably want to make special note of how this is different than the first. So highlighting the vehicle stuff, the arm weapon/ cannon thing, the ground tattoos, even coming out and saying "yes there are several traditional dungeons that will satisfy you if you loved OoT, MM, WW, TP, don't worry we heard your feedback". Maybe you are right that they are going to go light on the marketing with this one, given it will be guaranteed to sell 15 million copies. But still part of me thinks they are planning an E3-like media event either later this month or in April to hype everyone up and highlight some of the key features. That as you've pointed out, we've seen tiny glimpses of, but that is all.