I understand that nobody can know this, but people on HN probably have the best chance of being close to reality, so just try to imagine.
I doubt that somehow. If you used HN as a basis to guesstimate what the IT industry (hint the IT industry is a shit load bigger than the VC startup scene) is doing now you'd be way off, using it to guess what will be used in 5 years is like using tea leaves to guess the exact position you'll cut yourself shaving.
I want to know(or try to imagine), what will be used to build cool new awesome things in sexy startups, so I don't mind this kind of bias.
I'd love to see WebAssembly replace it, so that we can use better languages on the front-end, but I won't be holding my breath.