According to this Gamasutra report, Prope boss Yuji Naka is going back to his roots with a Sonic-style project.
“At Prope,” Naka told the site, “we’re actually planning on making a game like Sonic right now. We want to keep trying to make various kinds of games.”
Proper’s also working on Wii games Let’s Tap! and Let’s Catch! at the moment.
More through the link.