The Android navigation bar has always differentiated to iOS operating system, for giving us more options than the only button that has the iPhone. However, its design has changed over time, and Google may be working on a new design for the navigation bar buttons.
More modern, although less minimalist
The new icons that could be worked on Google for a future release would be something more modern than the current icons, although it is also true that they would lose something of minimalism. And it is that we take into account that already had been reduced almost to its maximum expression transforming into a circle for the Home button, a square for the multitasking button, and a triangle for the back button. In principle, it would retain the essence of these three icons, although they would be filled with color buttons, even enlightened, not like the current ones, which are only outlines of the geometric figures.
A new Home button
The button that would change most of all would be the Home button, as it will be a unique circle to actually be several concentric circles, with a light color. It would being clear that it is the Home button, and would be even clearer than with the icon above, because it would have more prominence.
Logically, this would only happen in those smartphones that will have an interface where the buttons were virtualized on screen. Either way, the design may change in a future release. Android N? Perhaps it is a surprise for the new version, when it permanently. If so, the recent Nexus would already have these new buttons redesigned Android navigation bar. Android N will land soon, probably throughout this summer of 2016.
The article Google could redesign the icons for the navigation bar was published in AndroidAyuda.