When did they "affirm" that? They've said a couple times that "Java at this time is the only way to build apps," etc. They never ruled it out for the future, AFAIK. Please feel free to prove me wrong, but I would honestly be surprised if you found anything.
Having been to the last several I/Os where the question is asked at the fireside chats, the answer has always been "right now...". No one is saying dump Java, but if we could get some native hooks through something like Dart, that would be pretty awesome.
"Java at this time is the only way to build apps" is the right answer for Android OS, because the Android OS is a combination of an app runtime and a Java middleware layer. Adding another runtime to Android would make it a second class citizen, or it would involve building a parallel middleware. What they really mean is that the result would be messy, and it wouldn't be Android-as-we-know-it.
You can, of course, move the Android middleware layer to other OSs, for Android compatibility. Which is how you can run Android apps alongside Tizen apps: https://youtu.be/nmiHPcHGgSM
Android was designed for one runtime, Dalvik and later ART. But there is nothing preventing a new OS being designed for multiple runtimes that includes runtime support for Android apps.
I'm generally not sympathetic to Java complainers. If you have Android Studio, or any other decent IDE, verbosity isn't a problem. But an OS built for Dart apps and a Dart UI stack would be the logical next step.
Having been to the last several I/Os where the question is asked at the fireside chats, the answer has always been "right now...". No one is saying dump Java, but if we could get some native hooks through something like Dart, that would be pretty awesome.