I personally loved Wind Waker, and is probably my favorite Zelda of all time, or at least tied with Majora's Mask. So its not like Nintendo has been gradually disappointing me since Ocarina of Time. The only console game that disappointed me was Twilight Princess and I think it was due to three reasons.
1. They took out a lot of beta and didn't tell anyone, so LOTS of the stuff I was excited for didn't even show up in the game.
2. I took every single screenshot and made these crazy ideas up in my head, like sidequests, minigames, etc, so much of the imagination took over reality and kinda made up the perfect game in my head, and instead of getting the game of my dreams, I got what they made.
3. They made the game trying to follow the fan's orders of a realistic Ocarina of Time, so instead of getting a brand new experience with Nintendo charm, we got a game too similar to Ocarina of Time without that unique quirky charm which I believe every previous Zelda had.
Skyward Sword on the other hand.
1. They haven't shown us any beta trailers or screenshots, just a simple demo area that was playable so they can't really get rid of cool stuff I've seen.
2. Since they don't have so much beta, there is less speculation, and I am much more aware of what realistically will be in the next Zelda.
3. This game seems very Nintendo charm filled, with its own personality. They are doing it their way and that always turns out well.
These reasons get me to believe that it will be a Zelda I won't be disappointed in. And as I mentioned, I am more realistic of its future values, and I am not speculating on anything. I am ready to take it for what it is. Now it won't be missing anything I expect from it.
So I have high expectations, but the game can't really disappoint me because I don't have wild assumptions about the game.