Iwata and Miyamoto said that they showed "Wind Waker 2" on that poster thing at the GDC to throw everyone off that they were making a cel-shaded zelda sequel for the GC, to add to the effect at E3. In other words, this is the "Wind Waker 2" that they've always been talking about, the second GC zelda, though not necessarily directly a sequel to WW. It does run off of a modified version of the WW engine.
"As long as there are dreamers who have the courage to follow their dreams, there will be heroes. And as long as there are people who pursue the unkown, there will be new stories to be told...and new adventures to be had." ~ Skies of Arcadia Legends

Proud holder of the fastest completion time of Super Mario RPG: 5:30:21