> I think it would be a major shock to the browser ecosystem.

To repeat the question from above, where is the downside?

Microsoft only abandoned EdgeHTML and adopted Blink because Google owned sites like YouTube were deliberately breaking in Edge.

At this stage I don't imagine they'd go back (to EdgeHTML as their engine) specifically, but it's not hard to imagine a world where MSFT maintains its own fork of Blink for use in Edge, Opera potentially the same.

As for Firefox: they get money for being the default search engine - if Google is broken up, the search engine company that emerges will have even more reason to want to be the default search engine on as many browsers as possible (and thus incentive to pay money to other browsers).