You can find out everything you need to know about Android App Bundles here. As this is a new way to deliver apk's I am very interested in how it works.
When taking a look at the explanatory video provided on the linked site you will understand that the App Bundle will only send the appropriate language resource files on download from Google Play.
Now, what happens when I change the system language after installation? Will the application not translate even if in the original App Bundle there was my language packaged?