Unless it just recently happened, no, he never promised a more realistic Zelda next.
He did promise there would be another Zelda on the Gamecube and said it MIGHT be more realistic.
I doubt it will be anything like the SW2K demo though. If it doesn't use cel-shading, it will probably just look more like Super Mario Sunshine. Not entirely cartoonish like Wind Waker is, but not really realistic either. But, considering how positive the reviews have been, I think the next game will probably be cel-shaded too. Most of the reviewers agree the cel-shading actually adds to the game. Assuming Nintendo pays attention to the reviews its games get, I think we'll see a lot more cel-shading from Nintendo in the future.