The “OK Google” hotword has already evolved from its inception, but as with all Google products, there is a lot more on the way. Android Police is reporting that the “OK Google’ hotword will move to an “everywhere” concept. The biggest addition will be with apps, which could mean that you will be able to search from within apps. The rumor is that it would be done while the app is opened, but I would expect it to be searchable even if the app isn’t active on your screen. For example, you might be able to add items to your favorite grocery list app via “OK Google.” We have been hearing about this type of evolution for a while now, so hopefully it will happen sooner rather than later.
The next part of the rumor is something entirely different and something that has never been reported. Google might be changing the current navigation structure in Android as in replacing the Home button with a Google Icon. In this configuration, pressing the “Google” button would open search, which begs the question of how you would get to the default home screen? Right now the thought it that it would be done through the recents, which doesn’t make much sense. The other interesting question has to be what other manufacturers would do if this does get implemented? Could Google mandate the “Google” button? Unfortunately we don’t know at this time, but since it would be a “Google” branded button, one would think they might be able to mandate it. We will have to wait and see.
source: Android Police