Currently, nothing. During Evil Plot #198: Adventure 1 I did mention that together with Chaos, we would reduce Station Square to rubble, and on its ruins I would build Robotnikland, the ultimate city!
My earlier plots were weird. World-domination. Done.
Only after this one, thanks. One will be plenty to manage. Perhaps if I can improve matters here so much that I'm no longer needed I'll move on, but for now, I doubt it.