What I see, as a web dev, is that finally Apple will have to keep Safari/iOS up-to-date with Safari/macOS, and that in turn up-to-date with all other browsers. I.e., they will no longer be able to artificially hamstring the web in order to prevent web apps from competing with their App Store.

They certainly have the money to keep pace with Chrome, and I certainly don't want to put up banners saying "works best in [anything but Safari]", which has been the case for many years now.