I wonder if you've ever heard of a product called Duke Nukem Forever?
Not to say that SGDK2 is vaporware, but rather, to say that it will come out "when it's ready" and that's all. Giving a date or even a ballpark may lead to dissapointment.
That said, BlueMonk has said (once) that it's about 60% done. This was awhile ago though, and it maybe more.