Today we know that the black hole problem isn't a problem. Black holes are not matter an energy sinks we thought they were. They're basically liquidizers. Matter and energy interact with them but don't vanish. It scatters, eventually coming out the other side. Nothing gets lost or destroyed.
So we don't need white holes any more.
The, "coming out the other side", makes more sense to me wherever that other side is. To me it would make sense that all that matter and energy devoured by a black hole could possibly pop out into a new universe in another dimension, but I admit I know relatively nothing about the science or theory that would support or not such a hypothesis.