The whole next chapter thing would be fine, I could deal with that.
The thing that's holding me back is that it's never just a new chapter, there's always alterations to the earlier games as well. What happened in them, what caused them, how they continued after the events.
I still don't see how that would make this worthless.
For example, if the Wii U Zelda game (henceforth, Zelda U) reveals new information about things that happened during the time of Skyward Sword, then that new information is part of Zelda U and not Skyward Sword. Skyward Sword came and went, and we finished the game knowing everything needed to for that game. The new information in Zelda U about other events (related or not) that transpired during Skyward Sword will no longer matter to, or have any impact on, Skyward Sword.
Additionally, no Zelda game has ever drastically changed or added to a prior Zelda game. They've only hinted at the connected history.
The only thing that will make this worthless is if Dark Horse pulled a dick move and released and updated edition, which contains everything int he first book plus more (making the first book irrelevant). I'm guessing due to the demand, they'll probably do that.
We are talking about an art book, are we not?
I had the import, and it had a lot of text in it about character backgrounds, history, etc. Not all artbooks are just art... I actually love these types of artbooks that delve deeper into the game/series.