Black holes are everywhere. There is a supermassive black holes at the center of every galaxy and there are over ~100 billion galaxies in the observable universe. There are also millions (if not billions) of other black holes that are the product of supernova explosions of very large stars (I'm pretty sure at least 10 times the size of our parent star). Black holes won't explode to create a new universe in our universe. But they may be birthing new universes in different realities. That is a theory that the opposite of a black hole is a "white hole" and that what we observed with the Big Bang is a white hole produced from a black hole in another reality.Hawking (or at least this video) is suggesting that black holes are developing as we speak and that eventually one of them will explode causing another big bang.