I will admit, I was a bit disappointed as well that Elantris didn't have a sequel. Now, I will also say that I thought the ending of the book was downright brilliant (always have). I thought it ended at an excellent point and really, the book is not about the war with Shu-Dereth. It is about restoring the power of Elantris. I mean, it's called "Elantris" and not "Fighting Against Tyrants". Come on, man, the main plot was resolved.
But, I was in the age of endless sequels. Things had sequels, so you expected there to be sequels. So, when I first read the Elantris paperback, it had a preview to Mistborn. I read the first few paragraphs, realized it wasn't an Elantris sequel, and I actually never finished that preview.
Despite my slight anger towards the lack of sequel, I never really found myself disgusted with the product as a whole. If you can't grin in wonder as the Elantris puzzle was solved, then really, you just picked the wrong book.
(And of course, as I read Mistborn, I was immediately engrossed.)
From my own novel writing, I suppose I would have "world-builders disease" in one of my settings. At one point, I thought I could write ten individual trilogies. The sequels and prequels were all natural extrapolations to the questions raised in the "first book". Like, when you introduce an item of infinite power, you should wonder how it was created. My thinking was there were more interesting stories to be told about how that item was created and how it related to other things, both in the past and present.
What that little anecdote shows is that there are always more stories to tell. Elantris, if Brandon so desired, could go on forever. He could tell numerous prequels about an early Elantris, how it was created, and the early days of AonDor. There could be stories about the origins of Shu-Korath and Shu-Dereth. There could be stories about the fall of the Duladen Republic (myself, I wouldn't mind reading more about Hrannis and what he did there, he's my favorite character). There are sequels as well, with Elantris now being restored. Brandon could write a story about rebuilding Arelon, much like he did in Mistborn 2, and that could also have a similar political overtone with fighting with Wyrn.
Personally, I would read those books. I like Elantris, and those sound like pretty cool plot ideas. But writing isn't merely about resolving plot points. You see, like my own writing, Elantris can go on forever. Thousands of years into the future, if you really felt like. Heck, you could write a story about Elantris in a sci-fi environment, maybe trying to reconcile technology with Elantrian magic.
The question of writing, however, is not to satisfy the author's whims of worldbuilding. Good writing and good sequels, in my opinion, should not just merely be the extensions of the questions brought up in book one. There should be new ideas continually forming to continue reader interest. Now, if there is a dedicated fanbase, there will be reader interest solely placed in the setting. But, I would hardly consider setting pieces very good.
I will first cite Isaac Asimov's Foundation series (which I wholeheartedly recommend for an intellectual read). It began as a trilogy, which was fantastic. Basically, it told about the huge Galactic Empire collapsing, and this scientist named Hari Seldon created the science of psychohistory, which could, in essence, predict the large scale picture of what humans would do. So, Seldon created this Foundation which, after a thousand years of tribulations, would form a new, greater Second Galactic Empire.
The Foundation series focuses on this Foundation and the tribulations it went through. Asimov's original trilogy ended only 200 years into the 1000. Naturally, fans wanted more, so Asimov wrote two more sequels some thirty years later. I thought the first of those two, Foundation's Edge, to be phenomenal. With that book, he didn't just increase the tribulations to the Foundation. He tinkered with the formula by introducing a separate entity from the two Foundations (I won't go into detail there, but Seldon created two Foundations), which was extremely interesting. The new idea integrated into that setting, I think, made it a fantastic book, and I would say it is even superior to the original trilogy.
Foundation's Edge is the pinnacle of sequels, where you both expound in setting and provide a feeling of new (and wonder). In this, there should be very interesting characters as well, which Edge also succeeded in. It was fantastic. Now, the Foundation series was so popular fans wanted more. He created Foundation and Earth, another sequel. I didn't like it as much as Edge, but it was all right. Now, the series continued to be so popular, so Asimov debated on writing another sequel. He had immense difficulty with even prewriting. I suspect this was because another sequel would only expound, but not add to the series as a whole.
See, Foundation never ended with the formation of the Second Galactic Empire. That was the ultimate end, and to this angry reader, he would be angry that the plot wasn't "wrapped up". But the ultimate end, I think, is actually quite boring. Just like many Hero's Journey stories, the end--the Dark Lord defeated--is not extraordinarily surprising. How it happened is. So with Foundation, the journey was more important than the end, too. Imagine a hero's journey story where the Dark Lord doesn't die, but it merely is implied he dies. You'd be angry, but you wouldn't be surprised.
Asimov caved into the fan pressure and wrote two prequels, and I really didn't think they were that great of books. Too much of the same old, so the sequels got boring and monotonous. In their defense, they had good "expounding" plotlines, but it really wasn't that new.
I'm also going to reference Lord of the Rings, though not in great detail (mostly because I am mostly ignorant on the subject). I would say Tolkien had world-builders disease. He has this huge world with thousands of years of history. Basically, all of the other side-stories in Middle-earth are really just expounding stories. Interesting? Maybe if you really love the world, but it isn't exactly a cauldron of new ideas, if you get my meaning.
I think Brandon does not want to write merely "expounding" stories. From what I've read of his books and his annotations, I don't think an expounding sequel would drive enough interest in him. It would require new, interesting ideas to motivate him to write an Elantris sequel.
Under this model, I defend Elantris's ending. Elantris ended by solving the main "idea" of the book--the thing that drove author interest--about the fallen Elantrian gods, which, I thought, made it very satisfactory (EUOL, feel free to correct me if I'm wrong about that). Because settings go on for infinity, really the only thing that can JUSTIFY an ending is to solve the main idea/conflict in the book. That's just good storytelling.
Maybe, Mr. Angry Reader, you just enjoy expounding-styled stories. That's fine. But I don't think Brandon is that kind of writer. In an Elantris sequel, I think you will see a lot more than just Arelon fighting Wyrn. That could definitely be an element, but I am absolutely certain there would be plenty of "new" to go along with that.
And I must say, in my own setting that I have, while I could write 30 novels, that doesn't mean it would be a good idea to do that. Stories must be interesting, so I could see 30 was WAY too much. I cut back severely, moving plot points around. In effect, I could see that the story itself could fit satisfactorily in one trilogy--even a single novel, if worked properly. Would there be more history? Yes. Would I probably know what happens later? Yes. But that is world-building, not book-building. Try to enjoy the story, not just the world the story is in.
