Not only is that not true, that's not the point of this article at all. It is only talking about speculation for when a L4 cache will be added to modern architectures.

> It takes a very small time window, and very limited historical awareness, to see Ln, for any n, as indicating anything special.

This article actually goes through the history of cache additions and talks about how it isn't special and more a matter of evolution. You seem to be arguing against points no one is making.

> it indicates what we have lately called "RAM" will now be called "L4"

This is a bizarre semantic game to play, since cache is fundamentally about a heirarchy of locality and main memory is a way for the entire computer to communicate through storage that may or may not use the CPU.