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.
Sure, it applies the browser security to it (so you have to break out a websockets proxy to send actual packets over the network, but that's no big deal for internal projects, and actually what you want for anything else), and you have to tweak little things but I find it amazing that you can go from pointer-manipulation-based low-level language with decades of libraries accessing all kinds of hardware, run it through a compiler and come up with something that loads in a HTML/Javascript page on a modern browser and runs more than fast enough to be useful.
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.