Right now the universe is expanding, with no indication of it stopping any time soon. Black holes would have to travel impossible distances and tremendous time scales to pose any threat to the universe as we know it. It’s more likely the universe will experience “heat death” as the end.
There’s a theory called the “Big Crunch” that this expansion may stop, and all matter — including matter locked inside black holes — may eventually merge, and perhaps create another Big Bang.
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