The 10th anniversary iPhone device aka iPhone 8 or iPhone Pro will be able to suppress the notifications sound is you are looking at it. Just simple like that. Well that is what Guilherme Rambo iOS developer says, taking that information from the early release of the HomePod firmware by Apple:
What @jsnell talked about on the last @_upgradefm is true: the iPhone will suppress notification sounds if you're looking at it pic.twitter.com/eFzKUfZYDx— Guilherme Rambo (@_inside) August 8, 2017
Before related post:
FACE ID FOR APPLE PAY CONFIRMED FOR IPHONE 8 AND IPHONE 7S.