I have been doing a whole lot of research on this on the internet and have been constantly keeping up with the Articles that are shown on Google.
First, a while back maybe like a little under a year that Mega Man's creator, Keiji Inafune, is working on an un announced Wii Title:
http://kotaku.com/gaming/capcom/inafune-on-mystery-wii-title-230163.php
I had thought at one point that this title was Zack and Wiki, but it is not because there are different people developing it.
This is an old article and no one hasn't heard anything since. As we know, Sega has been working with Nintendo with the development of "Mario and Sonic at the Olympics" Now that relationship and by the demand of the fans, Sonic is now a character in SSBB.
As we have it on Wikipedia, Rushan S. (2006-08-17). Sakurai and Miyamoto Comment on Sonic's Popularity. Nintendo Wii News. QJ.NET. Retrieved on 2007-08-04. “Nintendo hopes that Snake's appearance in Super Smash Bros. Brawl will encourage other publishers to allow their characters to join the Smash Bros. line-up, and is already actively negotiating for the rights to include at least one other non-Nintendo character.” While this article at least confirms there will be at least one more, which could be Sonic, I have read through message boards and such that there may be at least one more.
On Capcom's website, there was an interesting message given with all question marks. While I haven't found a person to crack the code, some people have manage to find the last word could be "Brawl" and the fourth to last could either be Rockman or MegaMan or the fourth and fifth word from the beginning could be Mega Man if you want to say it is two words:
http://blogs.capcomusa.com/blogs/news.php/2007/10/10/prepare_yourself
Also, there is a recent interview with Gamespot and Inafune talking about Mega Man's 20th anniversary:
http://www.gamespot.com/news/6179759.html
So we know that Inafune is working on a Wii Title, and given by the date of the article, it could be safe to say that he has been working on Super Smash Brothers Brawl along with Konami, Sega, and Nintendo all along. And since the anniversary is coming up on December 17th, we could potentially expect to hear the news soon if what I am saying has some true validity in it.
If anyone can support my theory with facts, please post it or say what you think.