Ios development is a walled garden. C# is barely used except to target Windos. Go? Too early to say. If it did fade away, who would miss it, really? Its express design purpose was to be not powerful enough to make big mistakes in. Has it transcended that? If so, what is its purpose now?
Java has shown staying power, despite its shortcomings, although its connection to the Apache Foundation ("where projects go to die") offers just a ray of hope.