Am I missing something here?
The game Duke Nukem Forever won't be completed, but it seems to me that the company 3d Realms still lives.
3D Realms are involved with games other than Duke Nukem. The 3D Realms website seems fine, and their online store is still up and running. You can still buy all their other games from them (Hocus Pocus being my favourite).
I don't see how one game (Duke Nukem) means the end of 3D Realms.