I don't think third parties are going to bother with RF protocol. They'll stick to the EF protocol over the RF interface (which mimics an adapted EF lens) as that's what they already know and has far less risk.
I don't think *true* RF lenses are really possible in the way that Canon lenses are - there's no capabilities for proper in-body correction etc.
I was loading lens profiles into my RP this weekend and noticed that the new EF 600mm lens cannot be loaded into the body with a message saying it provides correction+DLO data on its own already. Canon heavily implied that having the lens provide DLO data is an RF feature, but it seems that the 2 most recent EF lenses can do it as well.
Recent Sigma lenses already provide correction data, so it isn't a stretch to think that Sigma is working on having them provide DLO data as well.