i'd like to see them clean up the gestures so we can use the extra screen space at the bottom that the navigation bar uses. I don't see the point of gestures if all they did was remove the recents button.
A gesture to lower the top of the screen for one handed use.
Option to request pin or password to turn off the phone in case a thief wants to turn the phone off.
Improve Now playing. Make it easy to add the current song playing to your google music/youtube music playlist
Not sure if this would be hardware or licensed software but DOLBY ATMOS support to make good use of the dual front facing speakers.
smoother animations
improve sharing menu system wide like the one updated in google photos.