My reasons my be silly, but what would make me quit the game is if they kill off any more main characters. Then this game is going to feel like an episode of Walking Dead. If they kill Thancred or Alphinaud (HIGHLY unlikely, but still...) then I will be gone. SE always knows how to make good characters that you feel for. You adore them and care about what happens to them. So killing them off every few patches will start to tick people off. Sure it might make for great drama and/or tension, but at the same time it's depressing as all heck. But that's just how I feel.

Also, too much grind, farm, and RNG would make me quit too. I've thought about it a lot lately, but I'm on the fence about it. I love the game, love the story, and love the music. But the GRIND in EVERYTHING is starting to get to me. I probably don't need to very much, since I don't do any EX or Savage stuff. But even trying to get up crafting and gathering is a mess.

Anyway, sorry for rambling on so much. It's one of those days. xD

EDIT: I didn't see the post above me about Yoshi-P leaving the game. That might make me quit too.