Guava was always made available as Google's Java core utilities. I think it was always a misunderstanding to expect external contributions, like Apache Commons, as that was not its original intent. Rather it was to reduce internal duplication and ad hoc code with a shared standard. It then became useful for open-sourced Google projects (like API clients) and recruiting (new hires would be familiar with Google's libraries). Many suggestions are best spun off into new libraries, rather than donated to Google to maintain.
Java's many flaws have been papered over by a large ecosystem of libraries. As a non-gopher, I'm not sure if that same spirit exists. Perhaps that is due to the dependency debates, whereas Maven Central was quickly adopted when managing jars (via Ant) became too burdensome. Perhaps modules will help, as the language doesn't have to be batteries included.
