I am by no means a scientist,never mind a physacist but I do love the subject and the fact that,the law's of pysic's are common sense and a little imaganative theory.When talking about large stuff and keeping a safe dummys distance from the quantum world. Well we are missing 5 times the mass from out there in the vastness.Which is mostly dark matter and energy. Every galaxy has a black hole at its centre,of different size's and magnitude.Now I can't help thinking that the emence tempratures and pressures that exist within each one is going to change the nature and state of the matter that is pulled in,and a it should all be in different states depending on the numbers exerted in each black hole. Now this is where I take a leap of faith,out the other side,im a white hole comes the matter of a changed state,and depending on that state,defines what sort of universe or dimension that is formed on the other side. Thats what I love about pysic's though,I can only learn.thanks for reading this and please tear away lol.
Multiverse theory holds that other universes may exist as cosmic "bubbles" that may or may not "bump into" or in other ways interact with our own. So matter going in a "black hole," which is not anything like a "hole," and coming out into a white hole isn't a possibility. White holes are a mathematical expression that are not thought to be possible in reality. IF it were possible, the white hole would exist alongside the black hole and disappear as soon as the black hole absorbed even a speck of matter. On the other hand, white holes are theoretically conjectured to be the emitters of energy from other multiverses, though, again, there is yet no indication from observation or mathematics that white holes can or do exist in reality.
Just because we don't understand the nature of the universe does not mean that there is some sort of situation like the one you describe. People tend to build up elaborate scenarios around things they do not understand.
Think about some of the ideas that scientists devised to explain things that we understand quite easily today. The idea of the stars and planets all moving in perfectly circular orbits, but with intermittent retrograde motions is one such idea that seems crazy to us now.
I think that one day we will understand how things really work and it will not be so weird as you suggest.
They say the universe is infinite. When I start considering the possibilities of string theory, it literally gives me chills. I find it as frightening as any sci-fi scenario. It blows my mind, I guess you could say. It makes me supremely uncomfortable.