There are good reasons it won't happen anytime soon.
First, there are 2 kinds of Android programming: * majority of programs are written to Dalvik VM using either official Java SDK or with clever cross-compilers (I believe C# can be used with mono-based compiler) * for performance sensitive programs (i.e. games) code can be compiled to native ARM assembly. There's official NDK from Google based on gcc. However, those programs have very limited access to the system, pretty much enough to write games but you can't access majority of the OS libraries, since those are written in Java and compiled to Dalivk VM.
Go already has an ARM compiler so it wouldn't be hard to make it generate native ARM code compatible with Android, like NDK's gcc does.
Go, however, has a feature (concurrency based on goroutines/channels) that is fundamental to the language and just doesn't mesh well with traditional runtimes, which are provide good support for threads. Making goroutines/channels work on Java/.NET runtimes is either impossible or would have terrible performance.
Again, it's not inconceivable to e.g. modify Dalvik VM to also support goroutines but that's not easy and no-one is even talking about that being a possibility. Go is still a very young implementation, it'll take a year or two before the basics are worked out and then esoteric use cases like supporting Android will invade implementor's minds.