If they made some kind of fun event to keep playing, I might consider. Higher drop rates, Higher materia melding rates, instance waiting time removal, etc. I'd definitely try out some fun stuff like that, but otherwise not gonna bother. No point running a dungeon that will be changed or killing a primal that will be removed, that can't even be considered a "practice". Not to mention I would be pretty pissed if I ran a dungeon and got a Darklight drop that I won't be able to keep or something like that.