I don’t see why you would need to take away pixels for navigational buttons when SailfishOS has proved that buttons are really not nessecary if you instead use gestures. I myself have been using Sailfish (jolla) phones for about 2-3 years now and I find navigating on IOS and Android to be very slow beacuse of navigational buttons.
Navigation in Sailfish:
To wake the phone up you simply double tap the screen.
To close an app on Sailfish you just drag your finger down from the top. To access or peek at notifications you just swipe from the left edge two times (one swipe will get you to home menu displaying opened apps) no matter what is open.
To access app menu you simple swipe from the bottom.
To access home screen where open apps are displayed you simply swipe either left or right from the edge of the screen.
No buttons needed and more screen available.
This super fast navigation and the beautiful OS-design is why I’m still not sure if I’ll order the Librem 5. I feel that I will miss the navigation too much. But the development of the newer Sony Devices that Jolla decided to port to is going slow. I’d prefer that they had kept to their own models.