This sounds like Android phone manufacturers making fun of apple for removing the headphone jack and then doing it themselves a year later. Are they seriously going to maintain V2 support for a relatively small percentage of Powerusers which probably are mostly already using Firefox anyways? The point of being economically infeasible is probably in a month or so.
I think it comes down to how aggressive Chrome will be at changing the internal APIs that it uses. They could choose to make it a very expensive patch to maintain. But I think they would have to go out of their way to do that.
Firefox (and uBlock and BPC etc) works great on Andriod, but you have to disable Chrome to get Google apps to play nice.