How exactly is Javascript a promising alternative
platform to the JVM or .NET? Javascript is a language. Which Javascript platform are you talking about, that provides alternative ways to do what JVM and .NET do?
The JVM is getting better and better, by the way. Java 8 will be a better language with lambdas and closures. Groovy, Scala, Clojure, Jython, JRuby, and other JVM language implementations are currently great options for developing both portable desktop apps and web apps.
Not sure where Go fits into this either, Go is more of a replacement for C++ by and for Googlers who got sick of C++'s pain points.