For all we know they could be controlled by possessor Heartless, or simply living toys that are out to destroy everything in their path. We have too little information about them to know if they are controlled by an outside source or not. One thing is for certain, Gigas are a toy brand in the Toy Story world.
As for the topic at hand. I could see the unversed make their return, although in a smaller scale than Heartless and Nobodies. It depends on when and how Vanitas will appear in the story.
I do hope that Dream Eaters stays away though, they should remain in the realm of sleep and personally I dislike their designs with passion. As stated previously Soras encounter with the Dream Eaters at Traverse Town by the end of DDD took place in the Realm of sleep.