The short of it is that Huawei could opt to go for using and customising the open source version of Android, and use say the Aptoide app store (they are in negotiations) but this would by default NOT include the Google Play Store or Google apps.
But this is NOT the end of the world at all for users. Huawei (or other phone OEM) can still work their magic with their hardware and we'll be able to use the 3rd party app store to install most or all apps we are used to using (often more apps as some more "exotic" apps do not actually appear in Google's online Play Store.
If someone still wants to use Google's Play Store and apps they can download and sideload the GApps APK which then works like normal with the Play Store as before and installs all the Google apps. I used to do this all the time when I used CyanogenMOD as a custom ROM.
A little inconvenient maybe (just to set up once) but you'd experience more "freedom" and choice, and experience why open source Android was so important to have. It may well push Huawei onto bigger and better innovations so I'll be considering them as my next phone when the time comes. They'll also likely be ensuring their phones are not locked down so that users know they have to freedom to play with other ROMS.
I hate lockdown, I love freedom of choice. Restrict my options and I'm likely to buy elsewhere as a matter of principle.
See more background at https://mybroadband.co.za/news/software/306944-how-to-install-android-apps-if-your-smartphone-is-not-supported-by-google.html