Hi Alex Boschmans,
Thanks for your wonderful comments and analysis.
In context to the future of radial menus, as you have said that different input systems are a part of the environment and have a great impact on design. The usage of different menus like a radial, linear etc also depends on the input system i.e.., each has their own key advantages of maneuvering over the other and those key points help us define the system better.
I would completely agree with your hypothesis. As the new user has to become familiar with the system due to a learning curve. while the seasoned user has a higher learning curve and develops muscle memory.
Going familiar with a system will lead us to develop a mental model of use. For example for all the design tools present in the market have ALT key to perform copy action. The adept users are well aware of the same and are able to perform better.