Speculation: Bungie's next project is an MMO?
Now that is an interesting idea. Like Blizzard, Bungie has always been all about the possibilities of online play, and even though Halo 3 is not actually an MMO, there is no shortage of ways for people to interact with each other through the game– from Forge to the different coop modes, to the "XP" system in multiplayer, Bungie knows how to get people online and keep them there. And Bungie definitely knows how to build worlds– the Halo universe alone has inspired many books and countless pages of fan fiction and speculation, not to mention that there are big hints that it's connected to Bungie's other big series of games, Marathon. When you look at Bungie's past and the type of games that they've created, they definitely do seem like a great candidate to make a popular MMO.
Of course, whatever Bungie does next is up to Bungie, and, as Blizzard well knows, taking on as big a responsibility as an ongoing MMO can change a company all the way down to its foundation– for better or worse. But as much as he probably just made it up, Hardcore Casual is right– Bungie's got the reach, the funds, and the knowhow to create the next big virtual world. Whether they choose to tackle it or not is up to them.