It makes sense, to me at least, to keep all Gen 5 (Hybrid and Prime) in one Forum, as opposed to how they do it for Gen 4, because there's a lot of overlap, saves keeping up with more than one Forum, I enjoy reading about the Prime, and a lot of people don't really pay attention to the Forum audience and make posts for vehicles that don't fit there.
Aside from charging, for the most part they really are the same vehicle. So I think it makes sense to keep it all together honestly. People can always specify prime or not in their posts or thread titles.