BioWare - Sonic Q&A @ Wired

They're still not revealing details but Wired has an interview with the BioWare Doctors on their handheld Sonic project.  Without details, the answers are pretty generic:

GL: Though Sonic games have had some story elements to them, the franchise is, at its heart, a simple platform game. You run, you jump, you collect rings. How do you see that making the transition to a genre that is traditionally far more character and story based?

RM:  We plan on taking those core Sonic elements that fans love about games and incorporating them into a brand new adventure that will feature the best of both worlds: all the fast-paced action of Sonic, plus a deep and engaging storyline that will keep players on the edge of their seats.  By staying true to those Sonic elements that fans are already familiar with, and injecting our own unique BioWare flavor, we plan to make that transition as smooth and exciting as possible.