Black holes may harbour their own universes is the most recent article from NewScientist.com. The speculation is that "When matter gets swallowed by a black hole, it could fall into another universe contained inside the black hole, or get trapped inside a wormhole-like connection to a second black hole, a new study suggests."
Fascinating stuff. It goes on to say that a computer model gave interesting 'results.' "Böhmer realised that one set of answers looked like a so-called 'Nariai universe' – a mathematical model of a universe allowed by general relativity in which the universe expands in only one spatial direction. (Our observed universe appears to be a "de Sitter space" instead because it expands in all three dimensions, so that distant galaxies move away from us no matter where we look in the sky.)"
That de Sitter space is in itself quite fascinating and says, according to Wikipedia, "Our universe may be approaching a de Sitter universe in the infinite future. If the current acceleration of our universe is due to a cosmological constant then as the universe continues to expand all of the matter and radiation will be diluted. Eventually there will be almost nothing left but the cosmological constant, and our universe will have become a de Sitter universe.
The exponential expansion of the scale factor means that the physical distance between any two non-accelerating observers will eventually be growing faster than the speed of light. At this point those two observers will no longer be able to make contact. Therefore any observer in a de Sitter universe would see event horizons beyond which that observer can never see nor learn any information. If our universe is approaching a de Sitter universe then eventually we will not be able to observe any galaxies other than our own Milky Way and a few others in the gravitationally bound Local Group."
Clear enough. Good bye universe, I guess.