I tend to think of them both at the same time, imagination usually comes before the theories, mathematical proofs and discoveries. I'm just mindful of what is a theory, and what is law and those other theories that are widely accepted and have been proven mathematically in almost every situation.
The thought has crossed my mind, assuming the expansion of the universe slows down at some point to allow a reversal. Otherwise, it doesn't seem there are black holes big enough to affect the entire universe. Part of the problem we have now is that the black holes at the center of every galaxy don't appear to be massive enough by our calculations to contain its outermost stars. Assuming that is true, it shouldn't be possible for the entire universe to get sucked down the gravitational well of a single hyper-massive black hole at the current scale of the universe.
My personal hypothesis / musing stems from the unknowns of dark matter and dark energy. Knowing how many black holes (hundreds of billions of supermassive black holes at the center of every galaxy), and wondering what they do with all the mass in our universe that disappears down its gravitational well, the assumption is they would continue acquiring mass to the breaking point of physics, so what happens then? Maybe it all goes into a new universe, and our universe is fed through many holes in that universe or perhaps a different one, though our infrared telescopes would surely pick up billions of heat sources if that were the case.
There is also some physical evidence that needs to be scrutinized a little more. When a black hole consumes too fast, it spits pure energy back out into the cosmos at its poles, which means light actually can escape its velocity, furthermore it suggests that black holes may have a limiting factor, its very possible they can't grow bigger than the supermassive ones at the center of galaxies, whenever they acquire new mass, the black hole simply belches out energy, converting the excess mass in the process. Nature may very well have a safety system built in that prevents physics from breaking down inside the black hole.
There is also another theory I liked that depends on the big crunch theory, but by using quantum mechanics, the nature of the magnetic force will prevent the universe from ever reaching a singularity point and at a certain point the repulsion will create a new bang, and perhaps this has gone on over many cycles, retracting and expanding, recreating the universe again and again.
The universe's unimaginable scale truly fascinates me, these two links were posted on I FN love science on Facebook, they do a good job of demonstrating the immense scale of the universe from the tiniest particles to the estimated size of the universe.