So in Android P buttons are largely being replaced by gestures. Only the home button will still be used, with back available on a per app basis, and the task switcher square button being repurposed for screen orientation switching between portrait and landscape.
But HMD could decide to do something different with phones that have dedicated touch buttons like the Nokia 8.
Could HMD make the function of the triangle and square buttons customisable? Add multi tap options? If these buttons are also swipe sensitive then add up/down/left/right options as well?
Personally the more shortcuts and customisation options I have available the happier I'll be!