The article I read stated that "Barry'd Treasure" is a limited series, so I'm guessing it has a 13 episode run to start and they'll waiting to see how it does? It will air right after the Season 5 premier.
Also Darrel will be teaching Brandon the ropes during their "arc" if you guys remember they attempted to introduce a rift between the two of them last season which seemed forced and just plain meh.
Doesn't seem to be any additional new people, just Casey and Rene, and Ivy Calvin.
Barry's spin off also seems to be a reason why A&E continued to air promos with him.