A new level of density requires invention and experimentation. You probably can't do much more than double density without actually building a prototype. It's a

A new level of density requires invention and experimentation. You probably can't do much more than double density without actually building a prototype. It's also a function of cumulative spending at an industry level as no one is vertically integrated anymore, not even IBM or Intel: fab and test equipment separated from design from fab operator from EDA software etc... many layers.