I agree. Star Craft waited how many years before the sequel hit? Last I checked old and new gamers alike were hyped up for it. I honestly think DNF will sell like crazy and be huge news. Will it be good? That's the real question.
Starcraft is different. Many people still played the original for all of those 10 years. It was never irrelevant. Not only that, the series didn't go through all these hiccups and false starts (except for maybe Starcraft Ghost). Most people who were serious about RTS games played the original at one point because it was genre defining.
The Duke Nukem games, on the other hand, were decent but not spectacular. Not only that, it's a 20 y/o IP that was basically abandoned 10 years ago. Aside from the ever present rumblings of rumors, I highly doubt the average gamer knows or cares about the series anymore.
If it does ever get released, it'll get a bunch of fanfare at the beginning, but will sell poorly. Just look at the new wolfenstein game that came out last year. It sold poorly, and got mediocre to average reviews.