Go kinda is already, but is too sucky on too many levels to really break through.
Rust is still alpha and seems to be going backwards at times, but looks like a strong contender.
Assuming Go fixes its many problems, and Rust is eventually delivered, I think they will both have a strong role to play, Go in the networking/systems space, Rust in the large scale app development space (like making a browser).
But C will still be around.
Django/Rails Sinatra and so on.
These frameworks do injustice to their languages :
Rails hurts Ruby, Django hurts Python, Sinatra hurts Javascript.
JavaScript has a lot to offer but in the distant future. An even then it relies on slaves building pyramids.
Go is fantastic at what it does well, which is lightweight concurrency (with a synchronous api), something that no other compiled, imperative language offers.
But I haven't spoken to a single Go developer (and I've spoken to a few) who don't hesitate to tell me how sucky it is in many, many other ways. I've heard the phrase "I'm really starting to hate Go" more than once or twice.
Is there some JS framework called Sinatra? Either you made a mistake or I'm out of the loop when it comes to the JS world.
The only Sinatra I know of is http://www.sinatrarb.com/