I seriously doubt that a recall will never happen for this, because it's not a safety issue, and can only be seen if you lift the hood. I'm also doubt that every vehicles will develop the problem. Even if most of the FJCs get bulges, most will probably be minor enough that most people won't even notice it. I really don't see a need for a recall.
As for warranty issues, it really depends on your state's laws. Some will require them to fix it as long as it occurred before the warranty was out regardless. In other states they can get away with not fixing it after the warranty is over.
Toyota Warranty and Coverage