Speaking to Game Informer, Eiji Aonuma revealed that Sheik and Ganondorf will be resurfacing in Super Smash Bros. Brawl for the Wii.  Aonuma stated:

"I’ve been working with Sakurai for a very long time with this new Smash Bros., because the Wii came out and when discussion for a new Smash Bros. took place nobody could think of anyone other than Sakurai working on it. He was kind of the default, and I was very happy to hear that he would be working on it. Actually, my designers did work on the designs for Sheik and Link and Ganondorf. So they submitted the initial designs, and so it would fit in the Smash Bros. Brawl environment, they’ve had to tweak some of the designs. But Sakurai has brought those altered designs to NCL. We’re working very closely with the team of Smash Bros. Brawl to make sure the characters look their best."

Seems Aonuma beat Sakurai to the punch on this one.  Fans debating whether or not Zero Suit Samus would replace the Sheik character apparently have been laid to rest.  Now all that remains is to see the Sheikah from Ocarina of Time in action.  No word on whether Ganondorf will be based on his Twilight Princess version, but all indications so far seem to hint at this.