Could Android be getting an updated set of navigation bar icons in the next update? The folks at techIT seem to think so. An image leak suggests that the update to Android 4.4.3 will come along with a refreshed design to the icons in the navigation bar, with the back and recent apps buttons getting a new look, and the home button being completely replaced with a "Google" button that would presumably take you to Google Now instead of having the home button there at all times.
The belief though is that the Google button would only be there in one scenario, which is when you're already on the homescreen to begin with and essentially have less of a need if any at all for the home button to be there. When you enter the app drawer or open an app however, the home button would swoop in and take over the spot where the Google button would preside, allowing you to get back to the homescreen at any time. If the home button is indeed getting a replacement for an easier and more convenient way to access Google Now, there would certainly have to be a way for users to get back to the homescreen from other locations on the device. Whether this change takes effect or not doesn't really make a different for me personally as I use gestures and/or the pie controls from Paranoid Android to navigate between apps and home. Not everyone has that luxury though and will still need a way to get back to their homescreens when they want to.
As Android evolves so does Google Now and we're starting to see more and more functionality come to it. Google Now will be the base for the Android Wear platform to give users easy access to search and notifications, and Google Now is also becoming a bigger part of other Google products and services like Glass, Chrome, and Chromebooks as well as other Chrome OS devices. The appearance of the Google button could be Google's way of putting Google Now more into the limelight on smartphones and tablets now that it has evolved into a more solid feature. Thinking about the way current devices are, most Android phones don't have an emphasis on Google Now which would end up limiting its use by consumers. Placing the Google button squarely in the middle of the homescreen and alerting users to what its function is could make Google Now more known. It would certainly make it more accessible.