However, it seems that Defense Grid 2 will still be coming, albeit much later. According to the Kickstarter page, “We’ll need to do extra work on our end to earn or raise the remaining funds in order to complete DG2, but when we do, you’ll still be a part of the team. Crossing $250,000 gets you DG:Containment this December, and DG2 when it is complete.”
So, donors will still be getting Defense Grid 2 when it's done, though it seems developer Hidden Path will have to find another funding source to do it.