Pretty sure that as long as Io exist absolutely nothing OVERT will happen. Most of them don't really care for mortals like other deities, and its a known fact that several of them, in particular Bahamut and Tiamat, do other things on other planes as a differently named deity and as such would generally not care either. If Paladine/Bahamut is still barred from the material realm, why would Tiamat/Takhisis suddenly be allowed to? To add to it, Fizban/Paladine/Bahamut has according to lore, at bare minimum been introduced to our Earth, so its a high mark that he knows about supers, which would mean at some point Tiamat would too. But even if its a new universe, its still the material plane and those two in particular have some penalties associated with being on it...