mapi3
The question is more tricky regarding CPI ad networks or app analytics services. CPI ad networks will make less sense because the Installation disappears. Web technologies will make SEO easier for developers (app indexing was not easy) so paid acquisition and SEO will be back in competition... which should lower the ad spending. Retention remains key and app analytics and mkting tools (like push notifications) have acquired a great know how about managing users during their lifetime. So they should stay too.
Like in the 00's when developers had to adapt their skills from Windows software to web technologies, I assume native apps developers should start updating their web skills. It's hard to find the right guy for developing a high quality PWA right now.
Websites are much easier. We make a request in Google and load a website in seconds that gives us just what we're looking for! It provides instant gratification. It is also proven that people are more willing to stay engaged once they've received some value. Smart developers will know when they can ask visitors to install the app, receive push notifications, ...
With apps it's not uncommon that we don't remember why we installed it because the app didn't give us instant value. With PWA, users will associate the app with the gratification it provided at first use and will remain engaged.