Were Sora, Donald and Goofy confirmed to appear in Kingdom Hearts 358/2 Days?
If not, here's your confirmation:
That's apparently a retail promotional video for the game. The three appear past the 4:30 mark.
As pointed out by this blog, Donald and Goofy do appear to be playable. Sora is shown jumping around and fighting, but minus menus, so his status is hard to say.