Not much yet. I'd hold out. It seems the best sales are of short 3L.io's like rum.io or doc.io (especially doc which sold to Microsoft for 25k). I'd say 60-70% of the .io sales occur via Park.io and the rest on Flippa. Park.io sells their own .io's at the moment. Below are a few recent two word domains, then searching for games or game as a keyword (turns up no sales)...poker there were two sales for the same domain.