Capcom's Keiji Inafune - creator of Onimusha, Dead Rising, and the original character designer of Mega Man - thinks it would be very "interesting" to collaborate on a project with Halo creators Bungie.
Inafune-san was in the neighborhood of Bungie's Seattle studio (presumably for PAX) and stopped for a visit that had the Halo creators appropriately awestruck. Sure, Halo's a pretty big title, but this is the sort of resume you don't mess around with.
Inafune, who is currently "Head of Research & Development and Online Business" at Capcom, offhandedly mentioned interest in a collaboration when asked why he was dropping by:
Bungie is an amazing studio that has made incredible games. So I was always curious about how they made their games in hopes of being up to add some of the flavor into Capcom games. Also, I wanted to come down to Bungie in order to see just how well our philosophies on game design matched up. If things clicked, I know it would be interesting to collaborate together on a title in the future.
He talked about a good deal more beyond that - more of his philosophy and thoughts on game design, what he felt modern developers could learn from classic titles - but that above statement is the thing that really interests me here. Can you imagine the fruit that a Bungie/Inafune crossover would bear? Master Chief vs. Mega Man! Killing zombies with chainsaws, plasma screen TVs, and the Energy Sword! It turns out that Umbrella's virus heads into space and mutates where it creates the flood!
I don't know if it'd be on the same level as, say, Hideo Kojima's StarCraft: Ghost, but it could only result in awesomeness. ...probably.