I agree and believe that web apps will displace mobile apps someday. But the PWA concept isn’t enough for that. It should be improved, especially in such parts as a server-side code of the application and run-time environment. Usually, run-time in mobile apps is the functionality provided by an operating system such as file system, memory management, I/O support, installation/update precedures, etc.
Run-time in web apps could cover such things as, for instance, standardized ways to interact between server and client parts, browser independent I/O, standard frameworks, how we deploy apps on a web server and update them there, etc.