We have got a re-confirmation! Website The Magic Box reports that Tecmo has said that Ninja Gaiden will get a release on GameCube. An important reason for this is the fact that it's so easy to develope for GameCube.
According to the Magix Box, Ninja Gaiden will be a Zelda style action RPG.
It's also expected that the game will get an X-Box and a PS2 release.

Source: The Magic Box