Yes, go1.8 will be available on App Engine soon. We're currently in the process of preparing a go1.8 beta. Expect a public announcement and timeline commitment sometime in March.
I'm sorry it's taken us so long. We've had to address a number of problems around our release process which slowed us down. The good news is that we're running much smoother now and 1.8 is moving through the release pipeline as we speak.
I joined the team somewhat recently (hi!) and will try to be as open as I can in our communications going forward. I'm a software engineer on the Go runtime (as well as some other upcoming features), not a professional comms person, so hopefully I don't put my foot in my mouth too often :)