Nintendo power scans got leaked, its confirmed to be developed by Dimps & Sonic Team... basically dimps if judging by past history on collaborations
So.. Sonic Rush
More quotes from the legendary Iizuka-san from the interview
"From the start of the project, the concept was to bring Genesis-era Sonic and Present-day Sonic together. On consoles modern-day Sonic is best represented by action 3D-action games like Sonic Colors, which switch between side-view and head-on 3D perspectives. Oh handheld platforms, on the other hand, modern day Sonic is represented by games like Sonic Rush and Sonic Colors, where Sonic uses the Sonic Boost to run at high speeds. That's why we decided to use that style of gameplay from the handheld version."
"From all that we made a list of console and N3DS versions and divided them up"
History of dimps partially confirmed for handheld version. I'm sure by 3DS he meant DS.
Also confirms the HD version isn't all boosting
EDIT: Also says custom physics built by dimps