I don't agree Noel. If one looks across the water, one still sees lots of kits being produced and presumably built. Pure scratch building was always a minority sport.
The existence of higher quality rtr , simply means that " ordinary " modellers can experience the realism , that for many years was the preserve of high quality builders.
In fact with the arrival of resin castings, high quality etching and supplemented by 3D , and the demise of poorer quality rotary whitemetal, we could be entering a golden era of kits and scratch building.
Even in the uk , only a fraction of the prototype is available in high quality rtr, so there will always be a demand from specialist suppliers to produce kits and components
Compared to 30 years ago , when I last built kits , I would say there's a great interest and variety in today's kits and people who traditionally would never touch a whitemetal kit are building modern composite kits.
I think it would be a huge shame to see any reliance on RTR over any other method, in this hobby. We would loose one of the essentials of the hobby , that you " build " something
To give a concrete example , today , compared to 30 years ago , I can buy a whole series of components that allow me to fabricate very realistic track , complete with accurate tie bars , chair detail and good rail profiles. This suggests that track building is strong or even stronger then before