If Google decides to go full rogue and ignore W3C specs entirely and make up a bunch of their own shit, that devs then start to use because why not since the majority of their userbase use a chromium based browser, then Firefox can easily be taken out.

Which is basically the ending of the first browser wars, as far as I can remember. Internet Explorer had a little bit less market share than Google Chrome has nowadays, but still an overwhelming majority. Moreover, Internet Explorer had these IE-only tags and features, which further reinforced such things.

But here we are. Yes, Google Chrome and Google has an overwhelming majority right now, but so was IE (thanks to Microsoft's practices) back then. Google Chrome came at the right time with what people actually wanted at that time, and so was able to gain the upper hand, and eventually a chokehold.

My response though is more about "keeping things alive for its users", at least until such a breakthrough happens (maybe Servo has it?) or more pessimistically, until internet browsers fade away into obscurity (or perhaps just like IRC clients, it's still a thing, right?)