The game will be released for download on the September 22 for the Wii. Playstation Network gets it September 25th, and XBLA will have it October 1!
These dates are for North America ONLY.
...I guess it isn't coming out in September for the Xbox 360 after all. Who would have thought? Now people have to wait an extra week and some change to get their Achievements on.
In the meantime, you can check out Capcom's newly-redesigned official Mega Man webpage.