It's certainly possible that Wizards doesn't have any interest in public feedback on monsters, and MOTM represents a fait accompli. But I don't think we can determine anything about what will be in the One playtest packets based on past UAs. They've already included other material that wasn't tested in UAs, such as changes to combat, inspiration, and rests. And the D&D Next playtest certainly included monsters.
Also, considering some of the grumbling about the changes to monsters in MOTM, it would be sensible to provide an opportunity for large-scale public feedback. At least people would feel they had an opportunity to steer things, whether or not they did.