You can compile almost any language to JS or WASM.

As to HTML + CSS: it goes other way around: HTML and CSS (or rather its subsets) are being integrated into "normal languages", like Qt, Java. I'm not sure I ever saw any technology that could serve as a replacement for HTML + CSS. May be Eclipse RAP or Blazor? But they are so heavy that React will look like a butterfly and they're not aiming to replace HTML/CSS but rather just use it as output medium for their UI.