I'd rather see the series die. Don't get me wrong, I'm a huge fanboy of the original Deus Ex, I was quite fond of Human Revolution, and despite the harsh criticism I tend to direct toward Invisible War it wasn't a bad game (just a disappointing sequel). I guarantee the original Deus Ex has always had (and will always have) a spot in my top-3 whenever someone posts a "list your favorite games!" topic here.
The reason I want it to die is because I don't want it to get stale. What made the first one so great to me was the story. I've always been a big fan of conspiracy theories (they amuse the hell out of me), so the way that Deus Ex managed to weave together many different conspiracies and urban legends into a single, coherent plot has always fascinated me.
While Invisible War and Human Revolution tried to follow in the footsteps of the original game with weaving conspiracies into the mix, they ultimately fell flat to me. Invisible War opted to go the route of fairly generic science fiction storytelling while Human Revolution went for corporate espionage and civil unrest with the occasional nod to various conspiracy theories (like the e-mails from Illuminati members scattered around the offices in Montreal). It wasn't like the original game where nearly everything was grounded within a real-world conspiracy theory or urban legend.
The problem is that the original game was a little bit too comprehensive. It's no longer a surprise to players to find out that the Illuminati and Majestic-12 totally exist and are pulling the world's strings, for example, because it's already been established. Black helicopters, alien autopsies, men in black, freakin' alligators in the sewers and chupicabra? All covered. Where do you go from there to keep things fresh? This is why, frankly, I feel like Deus Ex should have been a standalone title rather than sequel fodder.
So I can't speak for anyone else, but for me anyway, I highly doubt another Deus Ex game would be able to capture what it was that made the first game so special to me. It's to the point now where I kind of wish they'd simply stop trying to, and create a new IP with Human Revolution's gameplay mechanics instead rather than turning Deus Ex into another series with yearly sequels.