blackcatatonic
Queen of Meme
They could just not have anything to announce. I mean, even if Firaxis are working on something, it doesn't mean that it's anywhere near an announcable stage. The supposed evidence of 'One World' doesn't at all indicate whether they were six months into the development process or two weeks, or whether they were just flying an entirely different kite using the Civ5 base or engine. The same decline of interest that you note as occurring in this thread would be much worse if they came out and said 'One World, to be released in November!'. Then there's the need to have confirmed details to append to what would otherwise be little more than revealing an already known name.
Finally, someone is actually talking some sense.
I refuse to believe an expansion is actually due out this year until they announce something to that effect.