Android Pie was more like Marmite because of the divisions it made with people who loved the new Android Gestures and those that hated it.
In my opinion Google decided to keep one foot in Marshmallow and one in Pie, it would make much more sense to go the whole way and ditch the buttons for good and embrace the gestures.
Thanks to Mishaal from XDA, we now know that Android Q could be a step in the right direction. They’re dropping the back button it seems and we may get taste of it this Year!
The Animation looks identical to Chrome’s when you use the Gesture we know and love; Swiping on the Address Bar to switch from tab to tab. The Gesture is smooth and buttery as you’d expect from Android these days… when this is ready, I can see that this will be a even more useful than the current set of gestures.
I find it irritating at the moment to switch between apps on Pie, it's almost like a Game where you have to be really quick to stop holding down the gesture to land on the right app.
The back button is what makes Android what it is, App’s don’t usually bake in a back button because they know there’s either a physical or virtual back button already on your Phone.
So I’m sure Google has been tinkering with the idea for a while now, but it hasn’t quite been ready to ship with Pie.
On one hand I’d be happy if they included in Pie but I’m glad they’ve not rushed out a botched version of it. So expect the Swipe-for-back to be polished when it comes.
If you’re eager to try out this feature, I'd put money on it being available in the upcoming Android Preview but we’ll have to wait and see...