Why not simply house any Airbnb, VRBO, HomeAway, etc. discussions in the existing Online Travel Booking and Bidding Agencies forum? It's in the T&D section and already hosts such accommodation providers as Expedia, Agoda, Hotels.com, Priceline and Vayama so expanding its remit wouldn't take it too far from its core or supplant existing topics. Maybe a slight forum name tweak to include more providers would clearly indicate it's increased role but why not expand an existing forum rather than creating a new one?
Merely MHO of course.