Microsoft's Kudo Tsunoda has said that it's not possible to release a patch in order to make older 360 games work with Natal.
Speaking during a Natal demo of Space Invaders Extreme and Beautiful Katamari at TGS, Tsunoda told D'toid that a "significant amount of code" would have to be altered in the games, therefore, a "simple update wouldn't be enough", forcing a publisher to re-release the game entirely.
Sorry kids. No Bomberman: Act Zero Natal for you.
More through the links.