App Engine's "standard environment" supports Python, Java, PHP and Go and the "Flexible environment" says the "supported" languages are Python, Java, Node.js, Go, Ruby, PHP, or .NET. Cloud Functions (beta) is nodejs only.
Given Dart's apparent popularity in Google (and the fact that it was created by Google), it's weird to see Ruby, PHP and even .NET listed as supported languages on a Google platform with Dart nowhere to be seen.
Dart seems like a natural fit for things like App Engine and Cloud Functions! Are the reasons technical? political? Is Dart not Mature enough? Is this likely to change anytime soon?