We have and have long since already had the web interface compatibility problem. This doesn't really change that, other than an unpredictable change in websites becoming more or less useful and compatible. Having Edge didn't make developers more or less willing to code for Firefox.
There seems to be quite a bit of speculation in this article. I think it's more likely that Microsoft will replace the engine in Edge from EdgeHTML to Chromium. They'll probably keep the name Edge, and make it look the same and have more or less the same features. (Though maybe they'll do a re-release with a code name, like Mozilla did with Firefox Quantum.) This makes sense to me from a business perspective, as it's much cheaper to use someone else's engine than to maintain their own, and functionally it makes little difference.
I make my kid use Edge just so I can see how good it's doing against other browsers (Hahahaha, this sounds like a real shitty thing to do now that I say it aloud). It's fast, I've never seen it crash. I could use it and live a fulfilling life. Whatever...
I'm fundamentally dependent on Chrome because Join lets me text from my desktop with it. If you're using Signal, on desktop it's a Chromium plugin. Chrome's a pig - it's a big, fat crashy pig. But until someone comes up with a decent desktop MMS interface, I'm stuck with Chrome.
https://www.theverge.com/2018/6/18/17475390/android-messages-text-from-web-feature If you use the Google Messages app, you can text from any browser. Not sure if it properly does MMS, but it's worth a try. I've gone Firefox earlier this year and haven't looked back. Solid, stable, fast. UI is kinda wonky IMO but not unbearably so.