I'd like to see a missing-mythology-monsters-only small bestiary next year, with world-over mythology monsters that don't appear in Bestiary 5 getting some love. 50 0f them would be lovely.
I'm not really a fan of inner sea bestiary, because of the unique creatures, the robots and the many too-much golems. There were only 10 creatures I used and liked in the last one.
I like the soft cover bestiaries, I really do. But what I really would like to see in the line for monsters is a couple more of the Revisited books taking 10 creatures related in some way and detailing them out to six pages each. We haven't had one for a couple of years now I'm starting to go through withdrawal. The last one was Demons Revisited, and that was well over a year ago. Even doing a Sequel to a prior one would be good. A Mythic Monsters Revisited 2, Mystery Monsters Revisited 2, or A Dragons Revisited 2 (particularly considering how scanty the information on the dragons is in Bestiaries 2 - 4 beyond the stat block) would be so nice. I know there are Dragons Unleashed and Undead Unleashed as well, but it's just not the same.
That said, I REALLY can't wait for both this and Bestiary 5, since I love monsters so much. [The six-year old in me is still very strong ;) ]