I agree feel writers will for the most part will forget this unless it becomes a true plot point. Need to see what he put about them. I bet it will introduce them, they are from other universes, something happens and they get written into ours as if it was always like this spoilers:end of spoilers
As how things went for Spiderman since it looks like that Multiverse spell is what caused this, with the Illuminati members being the only ones who know it.