Ian Flynn, writer of the upcoming Sonic/Mega Man crossover just gave an interview on Newsarama on the crossover and what to expect from it. It sounds like it will have much of what you would expect and want including a fight between the blue bomber and the blue blur when they initially meet. Makes sense, I sorta imagine it going like this.
Mega Man: Hello stranger, my name is...
Sonic: Oh shit a robot!
One part in the interview I thought was interesting was when Ian said this:
Flynn: There will be a number of "new" Mega Man characters insofar as we've not properly introduced them in the main book yet. And with the two doctors working together, you'll be seeing some new twists on some old ideas.
So it looks like some Mega Man characters will be introduced during this crossover. I'm kinda curious to see how that will play out. Either way this looks to be a shitload of fun and I can't wait.