The Legend of Zelda: Twilight Princess was (essentially) completed at the begining of 2006 and only a small team worked on it further to tweek it for the launch of the Wii. What this means is that there has been (roughly) 3 years since the last Zelda game was (essentially) completed.
I can't help but think that when Miyamoto said that the next Zelda game would play like nothing that came before it he was expecting the Wiimote controlls to be more meaningful than a waggle replacement for a button. I could be wrong but I suspect that problems surrounding Zelda development may have been one of the core reasons why Nintendo decided to move forward with the Wii MotionPlus.
Personally, I wouldn't be surprised if Nintendo announced The Legend of Zelda when leading up to the Wii MotionPlus launch and it was released as (on of) the big game for the holiday season 2009.
