According to the new issue of GamesMaster magazine (via Sonic Stadium) released in the UK this week, the magazine reports that Sonic the Hedgehog 4: Episode 2 will be released in “Late 2012″, which would see the title being released over two years after Sonic the Hedgehog 4: Episode 1.
We'd recommend taking this with a grain of salt and that you continue to keep this as a rumour, as SEGA haven't stated anything clearer than “2012″ yet.