Black holes do the opposite of what the Big Bang did, instead of expanding they compress everything.

I think that this might have been happening for a long time:

Big Bang happens - everything goes about for years and years beyond human comprehension - black holes become bigger and bigger, merging with one another - until at the very end there's only One insanely massive black hole and all the swirling matter around it eventually falls into its core - now this Black Hole contains the universe - it keeps being compressed until it is impossible to go any further and then explodes again into a Big Bang