http://www.sega.com/games/game_temp.php?game=sonicnext
Sorry, try again.
Even disregarding that, the lead designer of Sonic 360 is Shun Nakamura, who is a member of Sega of Japan, not USA. Furthermore, Takashi Iizuka is only mentioned in the "Special Thanks" section of the credits, whereas if it were developed stateside he would have had a much larger role, seeing as he's the head of Sega Studios USA.
The mouths of the characters are also synced to the Japanese dialogue, while in Sonic Heroes and Shadow they were synced to the English dialogue.
Just setting the record straight is all.
Back on topic, judging by Iizuka's question dodging, it seems Nightopians will be absent. It certainly makes sense considering the amount of development time they've had, but it's still kind of disappointing.