If Fedora is getting cold feet at the last minute the best solution would be to package ESR separately and make it available for people that don't really want to be "First". It's probable Mozilla will use the next ESR branching for similar invasive changes anyway now it's been set up.
And yes downgrading from current to ESR is going to cause breakage, but it's a bit late to change gears without breakage one way or another. Consistent breakage with upstream is way better than Fedora-specific breakage