That doesn't mean the franchise is dead though according to Gearbox CEO Randy Pitchford, who was talking at Develop 2015. As Eurogamer reported, Pitchford says that his studio is even open to collaboration:
I did not acquire the franchise merely so people could experience Duke Nukem Forever. That was, sort of, the toll to pay to give Duke Nukem a chance at a future.
The challenge is that Gearbox is very busy. A faster way would be if the correct developer would become interested and we'd work with them.
I think the question of what Duke Nukem looks like in 2015 and beyond is a peculiar one. I can't quite get my head around it. However, if a developer really has a passion for the franchise and a unique spin, I say let them have at it.