The problem is likely that Broussard wanted to make the DN game that would last forever. It would be perfect and without flaw. He did this instead of just shipping one in a series of polished games (which he could have made over the last decade+).
I remember when one of my friends was hired at 3DR and lamented when they were going about one of their engine changes. None of the art assets were usable after the change, meaning they could have just finished up the old game, shipped and then started work on the next one and shipped that too.
That first statement kinda reminds me of Xanadu... (wonder if they're ever going to call it quits)
The main problem with doing a sequel to a top-selling paradigm shift project is that the sequel by its very nature will not be able to repeat the paradigm shift and still stay true to the original. Or at least its so hard that there are very, very few examples.
I'd imagine that being part of that original team blinds you somewhat to the practicalities of releasing a sequel.
What I would love to see though, is all that unfinished work (if it is still around) being released to the public, so that duke enthusiasts can collaborate and "finish" some of the work to a playable standard...
I remember when one of my friends was hired at 3DR and lamented when they were going about one of their engine changes. None of the art assets were usable after the change, meaning they could have just finished up the old game, shipped and then started work on the next one and shipped that too.