I think that players want a Civ5 expansion so badly that they're grasping at straws and willing to believe any kind of speculation that new DLC or an expansion is coming soon.
I acknowledge that Civ5 expansion is
long overdue considering that the first Civ4 expansion came less than a year after, and the second expansion almost exactly a year later. At the very least Firaxis should've
announced an expansion by now, to drive up hype and interest in it. But there's been
nothing!
Some have speculated that Firaxis has been busy patching the game, creating DLC, and building CivWorld for Facebook

to develop an expansion for Civ5.
The latter seems the most likely.