UPDATE: Google reached out to us with some clarifications on the relationship between APKs and AABs. In a nutshell, the Android App Bundle is a new publishing format that Google Play will use to generate APKs specific to your device and has support for those new, dynamic experiences such as Play Asset Delivery and Play Feature Delivery. Google says that it also provides developers ways to download a secure APK version to be distributed on other app stores or sideloaded directly by users.

In other words, AABs won’t mean such apps can no longer be distributed in other app stores or as APKs, which is definitely great news for third-party app repositories. That said, there are still features like asset delivery and feature delivery that are tied to Google Play, so don’t expect to find those when downloading apps from other stores.