WebAssembly is great.
But I wouldn't want to code inside a browser IDE... for a start, once you start a project you can't close it or start another (that I could see!) - and I'd worry about what's being saved where.
But WebAssembly is amazing - you can do things like pull an old C99/SDL/OpenGL project out of the woodwork, tweak it minimally, and run it through a compiler like emscripten to generate a web page that just runs it. Graphics, fonts, sound, network, 3D, etc. all work within the browser environment, using just a standard webpage and the browser abilities.
In fact, since using such things myself, I can't understand why people are bothering with desktop applications for anything other than high-end, performance-critical things any more. You can do Sketchup in a browser, you can play games in a browser, you can watch movies in a browser, you can code business apps in a browser, etc. For the end-user experience, there's no reason that your code can't be brought across to the web even if it was written before that era.
Honestly, if I was a business requiring an in-house app nowadays, I'd just give people Chromebooks and locked-down browsers and a programmed interface using something like WebAssembly.