Google is working on a new Android kernel so they were planning in a long while to take full control and probably go closed source with newer Android versions.
They sheer developer power Google has at hand to throw at Android development, including out-of-tree-kernel patchsets, means that it is a very significant effort to just keep pace with them, and the AOSP "code drops" come late and require major integration work.
If they wanted to switch to a closed-source model, they could have adopted that for the runtime a long time ago, still keeping the closed-source blob on top of the Linux kernel.
Maybe the EU decision will change the benefit balance of Android "being open source", and Google will go on with forking off / replacing the whole middleware, but I think that with their speed of Android development most commercially viable OEMs only have a chance to follow by subscribing to Google contracts (and maybe getting early access to new releases) anyway.
Edit Also they will probably try to replace Java with Dart to get around the Java/Oracle problem
However, it might mean that they have to re-implement big parts of the Android runtime, or even do clean-room implementations by people not previously involved in those projects, to prevent legal attacks on the inevitably-similar code that results.
one may view Google's current emphasis on Kotlin in the same light
- GCC is no longer supported on Android, as of Android P
- Linux kernel is compilable with clang, but AFAIK not all changes have been upstreamed
- Project Treble made Linux into a kind of micro-kernel, with drivers using Android IPC to talk to it
- Fuschia doesn't use anything GPL related
Plus, I think the 5-year agreement it made with China to keep Android open when it purchased Motorola expired last year.
So I think Google was already planning to close Android. It was just looking for a good public excuse to do it.