Google's iPhone-like gestures will become mandatory in Android Q
The iPhone X's gesture navigation system
Android’s classic 3-button navigation system has served users well since it was introduced with version 4.0 Ice Cream Sandwich way back in October of 2011. But with screen sizes ballooning, bezels shrinking, and screen real estate becoming increasingly more valuable, it’s starting to look and feel quite dated.
According to Google, defaulting to just two navigation systems will help make app developing easier. After all, developers currently have to take into account the different navigation options offered by smartphone brands and how they may affect interactions with their respective apps.
UPDATE: Google has told Android Authority that custom OEM gesture navigation systems will still be allowed in Android Q, although it sees them more as a "power user option."
Things that are NOT allowed: