7nm is here to stay. 5nm is possible it is just an optimisation of 7nm SAQP and can be done without radical increase of maskset costs.
After that, we are going down the rabbit hole of EUV litho.
A poorly held secret in the industry is that fabs want to use EUV to not to make <7nm, but to make economical <40nm litho with single exposure.
The biggest increase in cost after 40nm were due to increased numbers of exposures and more non-device and metal layers.
Cheap 20nm, single exposure planar litho will be a very commercially attractive process for a lot of things.