Okay, so I just took his class at OUSA today, and gleaned a bit of information out of him.
He wants it out by the end of the year; he plans to have diagrams all done within two months.
He had us test-fold diagrams. He had three almost-complete ones:(missing arrows and/or words)the fiddler crab, wolf spider, and a locust. All three of them were well-diagramed, but I only had time for the crab, which came out rather well. He also had hand-drawn diagrams for the water strider and oak leaf. He said that he didn't want to "make Origami Insects 3," and will be limiting it to about 5 insects. He will have Attack of the Kraken and the Chimpanzee in it. He also mentioned trying to get rights for a few things, so he may have Sepiroth or one of his other trademarked items.
Be aware that even when Brian finishes all the stuff he needs to do, it's still often many months (sometimes many many months!) from that point on, as it goes through many edits, tons of work making it print-ready, getting the proofs done, printing & shipping, etc etc...
It's really not a fast process.
I've watched him make diagrams for things in a morning- drawing by hand from memory- which absolutely floored me. I know he's really fast, and good, so I have no doubt he's working faster than 98% of most folks would be able to even do. But even so, it takes A LOT OF WORK. cut him some slack.
And furthermore, please be aware that making books like this is really a labor of love... the demand for supremely-complex origami books is pretty small, and places like Origami House do it to keep the information alive for posterity as much as they do it for any business reasons. (If it was just about making $$$, we'd be swimming in easy 1-2-3 origami books 100% of the time.) So Brian's work on this book is really a huge gift to the origami community, and future folders- I'm sure he has other things he'd rather be doing that aren't quite as infuriating as diagramming complex origami folding sequences.
In any case, thanks Chan-chan, and I'll be buying your book as my first representational origami book! (mostly so I can finish that damn water strider...)