They're already using JavaScript for all new code, and gradually converting their existing code over using decaffeinate (e.g. https://github.com/atom/atom/commit/30cd83f7aa03c023e6103b64... ). But it's a reasonably big codebase and I imagine moving everything over incrementally will take a while.
What about moving to web assembly? Would it be relevant? Or is this a Firefox feature only? Or is this not interesting because the point is to write it in javascript?
WebAssembly will be supported by all browsers and JS engines, but it's not something you would use as your source code. I think at the moment it's more focused on high-performance use cases, e.g. rewriting a CPU-intensive function in C++, compiling it to WebAssembly, and calling it from your JS code. Or taking an existing C++ codebase and running it on the web without really using the DOM. But in the long run, I think WebAssembly will make it possible to do things like DOM interactions in other programming languages.
Instead of wanting projects to move to a language you know, you can better first learn the language they are written in, and try to understand their decision in the first place. If you know CS very well you would not be so eager to move to Babel transpiler imao.
There is also a nice comment in here about a large project that became a misery because of TS. Think twice before you hope!
They're going to have to support it in perpetuity, most likely. There are too many packages written in CS, which are relied on, and which are not really maintained so much.
