The rumors had been circulating for a while, that the next Deus Ex game might be in the works. We had heard that the name Deus Ex: Human Defiance was trademarked along with the website and other things for deusexthefall. At the end of March rumbles came out that we'd soon be hearing news about the next game in the franchise, and of course, come April 1st, we did.
Yeah, the next Deus Ex ... is an 8-bit April Fools joke.
The saddest part is that the tiny bits of demo that they made actually look really cool. They don't really make any sense whatsoever because of the events of Deus Ex: Human Revolution, but they look really neat. They jokingly ask for support for the game at the end of that video, but the thing is that if they really needed people to step up and say "make this!" then I'd be happy to, as would many others I think.
As explained here, they note that, "the Human Defiance name was registered on the off-chance it we might need it, but it was decided later that it wouldn't be used." Thus, it was repurposed for this joke" Whether or not that means that the other registered trademarks and things like that will be left on the wayside as well, or if there actually is a full fledged sequel or new game in the works.
At this point I really would like to see any sort of confirmation that there's another game in the series at least in the planning stages. It probably wouldn't hurt Eidos, and by extension, Square Enix either, because considering that it was monetary troubles that are causing the CEO to step down, they may need all the cashflow that they can muster.