Wii's E3 life pretty much parallels GameCube's E3 life. So at this time in GameCube's E3 life, both Reggie and Zelda debuted (2004). 2008's E3 was a downer, just as 2003 was (Pac Man VS).
If this E3 cycle is supposed to parallel the previous one properly, not only will the New Zelda be shown, but Reggie will announce Mini-Reggie(TM) or maybe his Ass-Taking Name-Kicking Reggie Twin Brother.
Considering Wind Waker came out in 2003 with a new Zelda shown in 2004, this cycle's 2nd Zelda is actually overdue.
And since Metroid Prime and Prime 3 came out in similar time frames, Retro's next project is also due this E3. If there was a brand new Metroid in the works based on MP3's engine, it would come out this November...