I found a leaked image of Android's new navigation buttons design. The Guy from the team of AndroidPolice have received this image first. You can see the new navigation buttons design above.
I found it from Citing report, they said: The Upcoming HTC Nexus 2016 phones might get a navigation bar makeover. It's still not confirmed that When we will get this new navigation buttons. I will soon update the link here to get this new navigation button on your phone.
Google made new colorful design with some animations on the home button for the navigation buttons. The new design is really looking very attractive. I don't have any more information as of now to share about new navigation button. But, will surely update this post with updates whenever I get any news for the same.
I think we will shortly get this new design in the next Android N update. Just keep visiting us, or bookmark our link to get the latest news.