We've seen more of zelda U now than we had of 3d world at this point relative to its release, so that's a point in its favor.
Unless Nintendo has a different secret game in the works, or is planning to use marketing to try to force another series to level up hard in popularity, I don't see anything even remotely comparable in potential popularity for this fall, so that's another point in favor of it making it out on time, though admittedly this would result in a rushed game if it were the deciding factor.
On the other hand, the appalling length of time between TP and SS, and the nearly-as-large length of time between SS and now makes me suspicious of how the Zelda team currently handles the development process. It's not like SS was some master-stroke that justified a full normal console generation of development time. Nintendo would probably have been better off making a straightforward TP sequel that released in half the time.
On top of that, the extra stress of HD development and the suspiciously-sparse nature of the teasers we've seen do make me worry a bit.
I do expect Nintendo to release a rushed version of the game this year if the full game isn't ready because the business situation still isn't very good, followed possibly by their original vision for the game in the form of a remaster as a launch title next gen.
