This has been a completely fascinating thread and as usual, I'm chiming in way too late, but two things:
The question of what (if anything) is extra-Universal has several mathematical and scientific speculations attached to it. One theory of mathematics says that there are numberous universes existing in separate dimensional spaces. We can grasp only four dimensions - height, width, and depth to perceive the things which are familiar in our universe, and time. Obviously, we perceive time as linear, but mathematical theory suggests that it might not be. There is a theory that everything that has ever happened or ever will happen exists as " the present" in some universe. Taken to its logical (or perhaps illogical) extremes, this would mean that nothing is ever lost; nothing ever really dies because it exists somewhere/sometime in some dimension.
Back to Jane2's question about endings and nothingness, the prevailing theory right now (until somebody comes up with the math for something else)for the end of our universe, is that it will go on expanding forever. The other alternative is that it will eventually reach a limit of expansion, then snap back like a rubber band that is pulled to its limits and then released. The problem with that one is that when the universe starts to contract, time would run backward, ending in a "Big Crunch," or a singularity - that infintesimally tiny point of dense matter that was censored earlier.
Those are just a couple of mathematical ideas. I personally believe in a God who has it all figured out, even if we limited human being, don't. I love playing with these ideas, though.
"And the postman sighed as he scratched his head, you really rather thought she ought to be dead..."