But even this statement is incorrect. FRP frameworks with Observables will remain useful in Java (as they have in other languages that already had coroutines). It's only the use of Observables as _an alternative for coroutines_ that is a transitional technology.
Maybe this is what Brian Goetz meant to say, but this is not what he said.
Yes, a transitional technology for the _Java Language/Platform_ post Loom. He never said anything about Functional Reactive Programming in general.