I think Sonic should take the Megaman 9 approach mixed with the Bionic Commando remake. I think we should see a Sonic 4 with 2D side scrolling along with 3D graphics. It would be kinda like the daytime levels in Sonic Unleashed, but strickly 2D. Not sure whether it should have the updated looks or the classics, what do you think? No werehogs, no mini games(except for the bonus zones of course), and no town hubs. It would be just like old times, it could be an online release(Xbox arcade, PS Store, or PC) or PSP game. It could have some new features so that it isnt just a rehash of past titles, but just small things that add to gameplay. Sub-boss fights could be Robonik's machines, while Robonik(can be eggman or original)tests out his own machines on Sonic himself for boss fights. I think Metal Sonic could be the sub-boss in a level and Scourge could be a sub-boss as well. The final battle after Robonik should be a all of Super battle between Scourge and Sonic. I like most of the new characters in the series, but I think to play them should be optional(Like Sonic 3 and Knuckles). I like Shadow and Silver, but not sure they would fit into the old style of gameplay. So sticking to Sonic, Knuckles, and Tails would be good and Scourge as an unlockable or DLC.

Thats my basic idea add and subtract what you like or dont. I just think going back to old school might be the only way to save the Sonic series and could be very enjoyable. It doesnt need Scourge, but I like his character.