Firefox unfortunately does not have the numbers on their side nor will they seemingly risk their Google payout deal. At this point, if you're using it, you're doing it because it has specific features or extensions you want, or you believe that it's ethically the right choice and you're comfortable with the trade-offs.
(I love Firefox, I just think we need to be realistic here)
Edit: I will actually note, in thinking after posting this comment, that it wouldn't surprise me if Apple was actually down for this proposal. Sigh.