No one knows dude, no one has said anything. Transitions require meter it's not free, so don't expect to see them much.
They cost two meters if you cancel a normal or string into one.
However doing them raw costs no meter, and from the looks of it, some are pretty fast.
If you meter burn a raw one, it costs one meter and gives it some kind of armor.
I'm 100 percent sold on stage interactions, but transitions I could go either way.
I like them in theory, but some of them have pretty long ass animations.
EDIT: if I keep them on, I would gravitate towards stages with shorter ones, like Gotham, and ignore Metropolis and Wonder Woman's stage.