Okay, so I have two Yubico U2F keys and two other U2F keys so far. I don't think I'll buy a fifth and sixth anytime soon.
But hopefully U2F will actually work in non-Chrome browsers in the near future.
But hopefully U2F will actually work in non-Chrome browsers in the near future.
I would guess you're referring to being able to log in to gmail (or anything in G Suite) with U2F from Firefox.
U2F is already available in the most recent version. See "security.webauth.*" keys in about:config. It just won't work with Google, at least not yet. Google's implementation predates webauth by a pretty fair margin, and from what I have learned, is different in small but important ways from the standard.
So we have a situation that drips irony: we have a U2F standard, usable via a standard authentication mechanism - and incompatible with the very web property that drove the concerted push for the technology's adoption.
Works fine for me.