As we see the world becoming what we nowadays call "mobile users", and apps winning over browsers, it is clear that this will have some effect on search and discovery of content and commerce. And potentially on Google's business since more and more "web/internet" sessions may not start in a browser but in some app - most probably email or Facebook. Getting traffic from there will be crucial, and one way to get traffic will be ads. No wonder emarketer is predicting that Google's mobile advertising share might fall from 82 percent in 2012, 68 percent in 2013 to 65 percent next year. And that apps - as a whole market - may overtake its volume soon.
Google, of course, may have to step up their mobile game with a) more emphasis on "googleNow" and b) something I have been waiting for for years - mobile app-to-mobile app-deep linking and deep links into mobile apps as search results. This means you need a better indexing of apps.