We're not entirely sure what to make of this, but here's what we know so far:
Sega has been teasing the reveal of "Project Needlemouse" since September of last year, which we found out tonight was officially an episodic sequel to Sonic 3 and Sonic & Knuckles to be released on WiiWare, PSN, XBOX Live Arcade, and a yet to be revealed mystery platform. Sonic 4 is abandoning the 3D platforming that has plagued recent Sonic games and going back to its 2D roots as you can see in the following trailer:
Where things get crazy is when it comes to a few details which will be unlocked when a few different timers hit zero on the Sonic 4 web site. According to SonicStadium.org and a post on NeoGAF, finding out what lies behind promo1_locked.png and promo2_locked.png on the web site was as simple as removing the "_locked" from the URL. Of course these files are nowhere to be found now, but here are the two images that allegedly were found on Sega's servers:
Now, it's entirely possible we're being pranked here, but, at the same time, Sega is revealing a fourth platform that the game will be on soon. Episodes of Sonic 4 are obviously being distributed digitally, and aside from the Wii, PS3, and XBOX 360, there really only is the DSi, PSP, and iPhone left that Sega would even conceivably release the game on... So, if nothing else, we've got a 1 in 3 chance of seeing Sonic 4 on the App Store.