I'd still give it another year before sales level off, or start to decline significantly. The costs are already coming down, and the big producers are packing these things with more options for less money. There are more showing up at one field I fly at, more for racing and using on an obstacle course. I would say within a year the furor over them being involved with the hobby, as well as being accepted in some clubs will be largely a thing of the past. What will be the first sign that this is on the decline....ads from Tower, HH, and HK will go back to fixed wing and helis.