Nothing stopping Google from publishing their own app in the App Store when this happens, much like how Bing has their own Maps app or Vimeo has an app even though YouTube is pre-installed on iOS.
In fact, that might even be better for Google. They've griped in the past about how Apple was slow to implement new features.
In particular, I know they hated the YouTube app (which Apple made). That's why the mobile site no longer redirects to the app - they wanted to be able to control the experience and iterate faster.
(I suspect the only reason Google hasn't terminated their agreement on the preinstalled apps already is because having YouTube and Google Maps on every single iOS device is worth more than fast integration of new features.)
In fact, that might even be better for Google. They've griped in the past about how Apple was slow to implement new features.
In particular, I know they hated the YouTube app (which Apple made). That's why the mobile site no longer redirects to the app - they wanted to be able to control the experience and iterate faster.
(I suspect the only reason Google hasn't terminated their agreement on the preinstalled apps already is because having YouTube and Google Maps on every single iOS device is worth more than fast integration of new features.)