Maybe. They say they'll go to the limbo of who ever they are sharing the dream with that has been to limbo before, which is only Cobb. His limbo could be stored in his mind, or it could be stored on the device and they just used confusing words about it. Either way, in theory, Cobb did go to limbo in that basement, because he DID die in the dream, and he doesn't get to spin the spinning top. Has anyone considered the fact that MAYBE limbo could just change to whatever Cobb expects to see? Or that everything was an inception performed on Cobb to make him forget about Mal :J