Sonny
Adventurer
After getting the 13th Age Beastiary I want the 5E MM to be something on par with that book--but I know that's pretty unrealistic as it's hands down the best monster manual I've ever seen. I'm not saying the 5E MM is going to be sub-par (I'm really feeling optimistic about this edition), but the 13A Beastiary really spoiled me.
I think I would prefer the MM to be as close to the Hacklopedia of Beasts as possible since that's my high water mark for monster books in terms of flavor(both writing and art design)/content/quality.