Just spoke to JAL, as I am on this flight in January and they are still 調整中 on the aircraft assignment. It is a possible seasonal switch but it has not been entered into the JAL system yet. If it s confirmed as a formal switch this month or next should see it entered in the system.
The schedule is normally released in August, so hopefully we should know soon.
I would say F being dropped is more likely than it staying once they stop selling it. It has been very much a no smoke without a fire in earlier cases. But let's see.