Doesn't matter. If it is lighter in tone don't expect people to attribute it to any sort of established narrative arc. It will be due to WB changing course.
If the lighter tone is done well, it still doesn't matter. That doesn't stop BvS from being a turd of a film on its own. Nothing will change that, even if JL magically turns out to be good.
If the lighter tone is done well, it still doesn't matter. That doesn't stop BvS from being a turd of a film on its own. Nothing will change that, even if JL magically turns out to be good.