<< This isn't the Duke that has been in the works for 5 years 🙁 >>
Right. The one everyone is waiting for is Duke Nukem Forever. That one has had release dates jumping all over for the last 5 years at least. Now I think the release date is "when it's done". That's what happened with Max Payne, and IMHO, that was worth the wait.
Duke Nukem: The Manhattan Project is more or less just something to give people more Duke to hold them over. If I remember right, it is kind of a side scroll or third person game. Also, it will be budget ware so you should be able to pick it up for about $20 when it comes out.