Sonic the Hedgehog 4: Episode 2 is the second part of the episodic game Sonic the Hedgehog 4, and is slated to be released sometime in 2012. It was announced by Gamespot via a teaser trailer, but not much else is known about the game itself other than a few bits of information. The first is that Sega has announced Tails will be in the game. This was first noticed due to a Sega Blog tidbit relating to a poem called "The Hedgehog and the Fox", which would refer to both Sonic and Tails. He was later confirmed in both a teaser trailer and the logo's official reveal. Metal Sonic will be in Episode II as well, shown in the secret ending of Episode 1 and the new teaser trailer.
Sega has stated numerous times that they have taken the strong feedback given to them about Episode 1 and taken it into account, resulting in a "new physics engine" and a "new graphics engine". Uncurling from ramps is also supposedly gone.
Sonic 4: Episode 2 is set right after the events of Sonic 4: Episode 1. After Sonic manages to destroy Doctor Eggman's newest space station, he goes off to find the doctor again, however, Eggman has a surprise in store for him this time.
In this Episode, Eggman revives one of his greatest robots, Metal Sonic. The second episode sees Sonic travelling through new zones, and somehow this episode will tie into Metal Sonic's original rivalry from Sonic CD. It is also known that Tails will join Sonic in this Episode, though how he will exactly has yet to be seen.
Sega has stated there will not be a Wii version of Episode 2 due to various reasons, probably the biggest factor being the Wii's filesize limit. However, right out of the announcement gate for Episode 2, they announced many other platforms they didn't have at launch for Episode 1, mainly the Android and Windows Phone platforms.