I'd recommend checking out PlayCanvas (https://playcanvas.com). It gives you a pretty powerful editor app to build WebGL content. It's got a scripting interface, but you can create some pretty cool graphical scenes without writing a single line of code.
Interesting. With a little hackery, it should be fairly easy to get this working with PlayCanvas. I'm not sure why it needs to use a new element type though (canvas3D).
I'm seeing a dramatic up-tick in companies wanting WebGL content to be built, either in-house or externally. WebVR is only going to accelerate this trend. So, sure, picking up skills around WebGL content creation should be a safe bet but avoid learning WebGL at a low level. Tools like PlayCanvas are there to help you get excellent results in a fraction of the time - you're much better off learning that.
Here is a hot code replacement feature: https://twitter.com/playcanvas/status/751469647149621248 You definitely learn JS! That's the language typed by the coder in the video. Of course, PlayCanvas has its own API to make certain tasks quicker and easier for you, but you can write your own shaders in GLSL if you like.
The engine itself is open source (MIT license): https://github.com/playcanvas/engine If you want a fancy editor to build more quickly, it's free to work in public. And for 'garage-outfits' that want to work in private, it's $15/month. I wouldn't call that serious dough. My gym membership is $70/month!
It's because Unity and Epic cross-compile large codebases to many MBs of JavaScript. This simply overwhelms the JavaScript engines on mobile. The PlayCanvas engine on the other hand is hand-written and is 125KB of JavaScript.
Have you tried it on your mobile? The fact you can experience this kind of content in the mobile browser and even mobile Facebook and Twitter clients without having to visit an app store is new and IMHO, very exciting.