So, that means they will never fix it?
I don't think there is anything to "fix".
For the last two years, the latest versions of Firefox have not worked on Windows XP RTM, Windows XP SP1, and Windows XP SP1a. XP SP1a support was dropped because maintaining it meant using an old toolchain for everything.
Realistically, nobody running a 13-year old Operating System should be surprised when they cannot run the latest versions of software. Nor should they consider it a "bug" to be fixed that the software doesn't run on such systems. And in this case, it's not as if there is no upgrade path- realistically my question to those affected would be along the lines of why they are still running XP Gold or XP SP1 in the first place.