If this project can pull in over a mil in 2 days then there must be demand. If those same people who donate to this buy a new Megaman then it would be in capcoms best interest. No reason why Capcom can't keep the project small and release it digitally it would easily make the money back and then some
There's plenty of reasons why. Do you think that if Mega Man really could print money like Sonic and Mario do that Capcom wouldn't be all over it?
The real issue is that for a real publisher this is a risk. Fans can be very vocal but they don't always put their money where their mouths are. We've seen plenty of examples of fans demanding games that end up bombing. Look at Sega Rally Revo: Fans were clamouring for a new Sega Rally, a new studio was set up specifically to make one and, for various reasons (some right, some wrong), people didn't want the finished product. The end result was that dev costs weren't reclaimed and SRS was disbanded.
If this game doesn't match people's expectations? Bad luck. You already paid for it. If a traditionally-published game doesn't match expectations? The publisher pays for it.
There's a massive difference between asking people to pony up the dev costs of your game up front in exchange for the finished product later and funding a project and hoping to make it back and make a decent profit out of it. For Capcom, a new Mega Man game doesn't make sense. For a crowdfunded project, it absolutely does.