Nintendo's usually quiet about all of their games until about one month before their release. System hardware is a bit different, but games tend not to get the treatment until they're ready to be pressed to a disc. I'm not seeing any shadier activity from them than there normally is. The reason why we got so much info pre-Twilight Princess was because it was originally intended to come out earlier. I wouldn't compare the current lack of info on Skywalker Sword to the info on TP at the same time since it's announcement.
A better comparison to their marketing campaigns would be PH and ST, and even look at the pushes this year for Metroid Other M and currently DK Country Returns. They're not the type of company to build hype over months and years. They like it all to come out in the window of the game's release so people are immediately made aware, and then they get excited and make a purchase. Other companies release a video a week or so for a year and eventually people's minds get fuzzy on just when the title's coming out, or they get tired of too much pre-hype.
So, really, it's just Nintendo doing what they do best. No reason to worry, or to be anxious. When the hype train starts, we'll know it, and we'll be playing the game soon after.