Because we've been screaming for it for months upon months now?

Plus, it's only 6 months until the public beta, at which point anyone who's pre-ordered can play it.  Need to get people interested in it by the time that date arrives!

We all rather know now and see what it looks like then to wait in ignorance. Moreover it's a way of doing business with stardock to get their customer input with the making of their games. If they want our input while they can still make major modification now is the time.

Diablo III does the same for example, so there may be a reason indeed.

If they did it so early, they may listen to players ideas and wishes. Some of them are bad, but some of them are very good. If you develop something, it is less difficult to add some features, if you plan it from the beginning. At the end of the development process it is often quit difficult or even impossible.

This.  So much this.

I've been doing software development for years, and it something that would take 10 minutes to change at the beginning of a project will take days or weeks near the end.

This doesn't only apply to code, but also to direction.  In effect, instead of trying to fix a broken system later, you ensure that it's built it correctly the first time.

QFT!

I keep hearing about a new Duke Nukem too. I wonder if they have release it...

Yeah why wait? Procrastinate NOW!

To give a comparison, Empire Total War was announced September 07 or there abouts, 18 months before its release next year.  Elemental was announced this month, approx 16 months before planned release date (I won't tempt fate by asking how final that date is  )

As for Starcraft 2, it was announced 18 months ago and will probably be out sometime in the next century if we are being optimistic.

Basically a developer announces what they are working on around this sort of time, maybe release a mini teaser trailer showing the concept and a couple of alpha stage screenshots, and then occasionaly reminds people what the project is about over the next few months before starting proper hype etc when it's nearing completion.