Ok, BAT is #23-25. Apparently #22 will be time travel (JB said probably the one before the BAT).
So, 18 is MM, 19 is Wrestling.
JB mentions "character development" (no reason it can't be the same of one of the others) and a dragon book, but also a "revenge" story against the BC (or so I understood).
I am not happy with extra books, personally. The larger the saga the more probable that I don't live to see the ending. But I want the story to be good, no matter how many books it takes.