Grargar: The Duke Nukem games have been removed from sale across all stores, while Gearbox (the new owner) is sorting out all the legal stuff that have to do with the transfer of an IP. The games will be rereleased on stores that Gearbox has signed a deal with (like Steam). As for their return here, it all depends on whether GOG will be successful in signing a deal with them.
Yup, just be patient while GOG works out a deal with Gearbox. I'm pretty sure Duke Nukem will be back with a bang, though i'm unfortunately unable to estimate how long & when exactly will that be.