What will Bungie's next project be?

This is my first post on rampancy, though I've been a long time fan of the website, I just recently created an account. One thing on my mind, is that I've been wondering what Bungie's next project will be. I'm sure loads of people are wondering. When Frankie was asked if Halo 3 would be the end of the Halo story, he was quoted saying "It will end this story arc." But what does that mean? Will there be a new game with the Master Chief? They can't just leave Master Chief floating in space can they?