It might not be hardware anymore, but there is still a ubiquitous back button. And depending on how you look at it, the rotation change could be a good thing - the intention is to keep the ubiquitous button set closest to where your hands will be resting.
It's not though. The back button on phones stays on the top or bottom edge (the icons just rotate to face you). Which side it will be on is wild guess though depending on the phone and OEM.
Tablets will move it to the bottom in whatever orientation you are in which good but the issue with that though is that the screen dimensions change and I can't tell you how frustrating that is in games and changing their OpenGL projections on rotation. Not only do you have to handle rotating your content for the orientation, but then you have to adjust for the screen size virtually changing sizes. For some games and apps (like ZenBound) this breaks things by moving the virtual center point of the screen.
