Just watch: The last world is the "real world" where Kamen Rider Decade is a TV show, that's why everybody goes around cheering when they see who they think is Inoue, Murai, etc. and asking for autographs. "Daishocker" turns out to just be a metaphor for Bandai, and the mystery man is [HIDE]Ishinomori[/HIDE]
Let's hope they don't recast Black...that would be stupid. And seeing how Kurata was listed as Black in the cast list of the movie originally it would be safe to say that he will be Black.
I fear a Doppleganger Black...to me that's kinda stupid, why not just have him travel to Black's world and lose his RX abilities...
Kotaro becomes Black at night because theres no sun.
Kotaro becomes Black RX at day because of the Sun.
My theory.