On the subject of prestige classes: it would not be worthwhile to design and implement prestige classes when you could never take more than 3 levels in a PrC at any rate. It'd be a waste of time.
Personally, I am sure that, once Josh releases TBH (whenever that may be), others may take the module and add m ore stuff (like PrCs) in. But I don't want him to waste his time on such trivial issues; I want the game to come out so I can experience the story and the characters. And, yes, I am this eager even after being spoiled about a good part of the story.