They have patents for screens full of holes that should allow a speaker and microphone to work through the screen:

http://www.theverge.com/2017/1/10/14225872/apple-patent-oled...

There is another patent regarding the TouchID sensor working through a screen:

http://appleinsider.com/articles/16/10/04/apple-patents-fing...

The front facing camera is a bigger issue.

With the right sort of directionality you might be able to get away with having the speaker on the top side and the mic on the bottom, leaving the whole front panel for the screen.

Or be super cool and have a mechanical system that pops out a little speaker at the top and a little mic at the bottom.

Maybe it's just my generation but me and pretty much all of my friends have not made a POTS phone call in at least many years traditionally; none of us know our phone numbers nor use them day to day.

If I end up actually calling someone (and pretty much everyone I know despises this and will do anything possible to avoid it) it's usually by tapping their number on a web page or in an app like yelp.

Bluetooth headset. Wired headset. 'Hey Siri' voice control. Apple Watch with headset.

Why would it stop you making a phonecall?