Well, that's just the thing. Facebook's control over React means it won't be left out of this. Why do we think that they invest in this? Every company wants to integrate themselves as an irreducible dependency in your processes and systems. Facebook doesn't get any money for letting you use React, and they no longer get the value of using it as a kludge to allow them to more easily steal the intellectual property of small inventors (not that they needed anything extra on that front anyway).

The continuing value added to Facebook's bottom line by React is in granting influence far outside of their natural scope. Could they counter Mozilla's move by introducing new React "features" that Mozilla simply "can't support" yet, even though they "really super duper hope the new featureset can come to Gecko-based browsers next year"? Even more insidiously, could there possibly be some little snafus in their QA process that let bugs that affect Gecko-based browsers go unnoticed?

That's their leverage, that's their retaliation against Apple and Mozilla's moves to stymie their flow of user behavioral data. But, I'm sure a company whose revenue stream is wholly predicated upon reselling user identity would never do something "shady" like this to prevent competitors from blocking their access to the data that forms the lifeblood of their product, right?

... Right?