First, that's not particularly relevant to the question of what happens to the browser itself. Second, the field of "things you can run that is not Javascript" when not in the browser is already incredibly rich, so we already live in a flexible world. Third, frankly I'm not particularly overwhelmed by the prospect of Javascript's longevity in the server space being a long-term phenomenon... an awful lot of what gets linked on HN is less "cool things to do with JS" and "how to deal with the problems that come up when trying to use JS on the server".
And fourthly, and why this reply is worth making, bear in mind that if the browser becomes feasibly able to run any language, rather than having Javascript occupy a privileged position by virtue of being the only language, the biggest putative advantage that Javascript-on-the-server has goes poof in a puff of smoke. If Javascript has to compete on equal footing, it really doesn't have a heck of a lot to offer; every other 1990s-style dynamically typed scripting language (Perl, Python, Ruby, etc) is far more polished by virtue of being able to be moved forward without getting two or three actively fractious browser vendors to agree on whatever the change is (just look at how slow the ES6 has been to roll out, when I'd rate to contain roughly as much change as your choice of any two 2.x Python releases). And it has no answer to the ever-growing crop of next-gen languages like Clojure or Rust. Without its impregnable foothold in the browser, Javascript's future is pretty dim. (In fact I consider the entire language catagory of "1990s-style dynamic scripting language" to be cresting right about now in general, so Javascript's going to be fighting for a slowly-but-surely ever-shrinking portion of pie.)
Depends on how JS evolves. It got a pretty serious setback when ES4 blew up and everyone went back to the drawing board on ES5 and ES6; the ES6 launch makes it (I think) better for most use cases than Python/Ruby/et al, because the VM is an order-of-magnitude faster than most of the popular choices and ES6 is a reasonably usable language even for someone unused to Javascript's current quirks: it has a real module system, the class syntax is sane and similar to how every other lang does it, the confusing `this` binding is fixed with arrow-functions, generators and Promises get rid of deeply-nested callback chains, `let` and `const` get rid of confusing variable hoisting, etc.
Google and Microsoft are both very seriously experimenting with typed variants of JS (TypeScript from Microsoft and SoundScript from the V8 team), and Mozilla had in fact already proposed adding static typing back in the ES4 days, so I wouldn't be surprised if the next couple of versions of the ES spec include static types. The future for JS is brighter than you think — although it's brighter only because it looks like JS will become a better language, not because of JS in its current, mostly-still-ES5 state.
