Sonic 4 Episode 2 is still a short way away, Summer this year to be precise, and people are once again getting rather excited about it. Sonic 4 Episode 1 managed to disappoint some people, and this time round SEGA thing that those people will be happy with the way the game has been made.
At this point, however, there are no plans to continue the series if it's successful. Speaking with Digital Spy, Takashi Iizuka discussed the future of the series.
"We are looking forward to hearing the feedback from the users for Episode 2, but we are currently not planning to release another episode. We just want to see how the users accept this episode."
That doesn't mean that there won't ever be any more, but that if people on the internet whine about things like Sonic being slightly the wrong shade, the series may come to an end forever. Can we count on people on the internet not whining? Only time will tell.