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Go is a major new language that is newer than 20 years old.
Instead of focusing on the actual languages you should look at the functionality of programming languages and how that has developed over time. The current versions of FORTRAN, C, Perl, etc. are massively different than their original incarnations.
For example, the move from a procedural methodology to object oriented methodology, the introduction of interpreted vs compiled languages, the general trend to move to higher abstraction, memory safe, untyped languages. These are all trends that are a) more important than "what language are you using" and b) often happen to a language. Just look at how Apple has taken C++ and bolted an unholy mess of functionality to it. They have already pretty much eliminated memory management and I'm willing to bet that type inference (or rather making Objective C un/weakly typed) is next on the to-do list.
Languages get extensions and improvements all the time. Imagine the inertia of staying with an existing codebase.