I feel you're being a bit unimaginative.
The entire series could take place over the course of a week and we could be no closer to knowing if NG was winning or not.
Or it could skip around in time.
We've tons of characters to check back up on. Again, think of Erikson's Malazan.
Prequels!
There's more than one way to tell a story, and far more than one story to tell.
FWIF, I doubt we'll ever know the final fate of Earwa.
Oh yes, the boy wondering through the wilderness, Bakker Magnus opus on philosophy.
Bakker wrote TUC as his Magnum Opus, though by definition one can't really define that until its pretty clear nothing else eclipses that work. He spent his whole life writing so he could get to, and tell, the story of TGO/TUC. So, the rest of gravy.
And, who do we have to go back to but those that where there at the end?
That whole story line (ie everything in Earwa other than The Great Ordeal)was a cliffhanger ending.
Have you forgotten about Meppa? Zeum? The actual fate of the empire? ... Just to name the obvious ones. I'm sure there's plenty more.
Why the instance that there must be nothing left but to follow around the dead ordeal?
In fact, prior to TUC, not one person would have expected TSTSNBN to be a trilogy of tales of different characters e experiencing the end their world. Not one.
That's a pretty bold statement. I disagree completely, there have been prediction of TUC rising and TSTSNBN being about that for a long time. Not that I called it either though.
Why can the world of Earwa only exist the way you have chosen to see it?
I did read your whole post, that little toss in at the end didn't convince me. 
Fair enough
Bakker said what he wanted to do was set out and give a story where a meaningful world becomes meaningless.
I'm just more confused now than before. Doesn't it make sense, that if Bakker's idea was to kill meaning, that TNG is about, well, TNG winning and meaning dying? Where does humanity redemption come in, if that's the point (which I believe you just claimed)?
We're not even there yet. Sorcery still works, the Outside is not shut. If, what he wanted to do was show the crash space and the end of meaning, he did a pretty good job with TUC with that. I don't know what else you would need to add. In fact, if there is no hope for humanity, writing post resumption, would probably ruin the series.
As I said above, there's still so much in the universe of Earwa that is left unexplored and unexplained. I guess for those of use who still aren't so sure of how everything works, there still a lot of interesting things to be written about.
If you've got it all figured out, I can see how more would be a waste of time, I'm just surprised that this seems to be your stance.
I'm also not clear why these things are mutually exclusive: Why, if there is no hope, is there no story left to tell, but if there is hope and it works out how you want, then all of a sudden there's stories left?
I guess what I'm driving at is why do you have to be right in order for there to be a story? It seems that either way there's plenty of words to read, wouldn't you agree?
Because, then it becomes a philosophical circle-jerk. Ask Erikson how well that worked out for him.
Not much to comment on. I'm not really sure how you got to this conclusion, but I'm pretty unclear on what you want or expect from TNG.
Prequel? Sure. Lots and lots I would love to read about. I'm sure ill read whatever is TNG. But, if what you believe is what we'll be reading, Bakker has set his self a high bar.
So, if yes to prequels, why do you not want or expect more world building, more stories, in TNG?
