I don't see it. There's no way to tell for sure whether or not it'll be a good game until we actually play it, but so far I don't think we've got anything to worry.
Miyamoto is pretty much fully involved in this game. He hasn't been fully involved in the production of a Zelda game since I believe the original LoZ, which was considered by MANY people back in the day to be absolutely amazing, and there are still plenty fans of it I believe. And then you've got Aonuma, who created the masterpiece known as OoT the first time he was involved in the development of a Zelda game if I've got my facts straight. You've got two people who've created masterpieces for their time on their first try working together for this game.
And then you've got the new style. Sure, we don't know exactly how the game'll feel what with all the Motion Plus stuff, but those of us who've played Wii Sports Resort definately have a vague idea of how the Swordplay and Archery will work, and everybody will probably say it feels absolutely amazing.
Then you've got the developers saying the game will be harder. This is bound to please the hardcore fans and they're sure to keep things easy enough/incorperate an optional help feature or something like that to keep the casuals pleased (like with NSMBW and SMG2, they were both plenty hard but they were easy enough to just play through and they had a help feature just in case you needed it).
Then you've got the developers saying that they're going to be changing the formula to make it fresher (EG dungeons without bosses, bosses without dungeons, dungeon/field/dungeon doesn't apply).
And then you've got them saying there's gonna be a smaller overworld, but it's gonna be denser. This can be interpretted as a more lively and content filled overworld than, say, the overworld of Twilight Princess or Ocarina of Time (they have two of the bleakest and emptiest overworlds in the series) and more towards something like the overworld of ALttP or MC.
Honestly, I only see reasons to be excited and not scared.