Here's a crazy, out-of-left-field, WTF style rumor: According to "mysterious sources" quoted by game blog Destructoid, 2K games is working on a BioShock MMO. Although there's little evidence of the truth or falsity of this rumor, it's an interesting idea.
I'm on the fence as to whether an MMO set in the city of Rapture is a great idea or the worst idea. Rapture in the first two games is such an elegant and weird place, I'd love to "live" there full-time, but on the other hand, nothing ruins the strange and mysterious more completely than sharing it with a bunch of normal people. Imagine a room full of Splicer avatars with names like "DarthVader443" testing out the new dance animations or gossiping about the relative merits of different plasmids.
Anyway, we've consulted with our super-rumor-computer and have determined that this rumor has a 43 percent chance of being true.