Following up the first report, some more details about what to expect have been given.From Ken Penders:
M:25YL is a reality. I turned in the script for the second installment and am working on the third while Steven is busy pencilling the first part.
I just planned out the first two years worth of stories and to give you a small hint of what to expect, there will be plotlines dealing with Knuckles’ relationship to Lara-Su, echidna democracy dealing with the Acorn monarchy, Nicole’s true purpose, Lord Rotor of Knothole, Knuckles’ sibling and other interesting developments too numerous to get into.
In fact, the closest thing to a villain doesn’t even show up until part 12 or 13. And no, it isn’t Robotnik or Dimitri, either. (Now that I think of it, it may even be a totally new character. I haven’t quite decided as I’m not sure how I want to play that out just yet. I’m having too much fun with all the other plotlines I’m putting together, such as the one segment entitled “My Dinner With Sonic”.)
Source: Ken’s Comic Book Stories & Art