Annihilus' original pretense for attacking the Marvel (616) Universe was that it was expanding into the Negative Zone and threatening that universe's continued existence. Universal expansion isn't a new concept, and nobody ever said Annihilus was lying about it. Personally, I think he was telling the truth.
So let's say the 616 (616, 616) universe really is encroaching into the Negative Zone. What is that going to lead to?
The Crunch is the place where the universe is expanding, so in theory, that must be where the universe is meeting the Negative Zone. Based on what the energy did to the Silver Surfer* [*Ed's note - see Annihilation: Heralds of Galactus #2, true believers!] after only a few moments of immersion, I think we can safely conclude it's pretty damn destructive. If it's anything like that on the other side, then I'd figure anything that happens to run into it would probably go bye-bye. (Quick thought: the Kyln was a prison that also served as a power plant, harvesting the energy generated by the Crunch, and distributing to several planets. If the Crunch is constantly moving with the universal expansion, then the Kyln has to move with it, right? Then the Kyln is constantly getting farther from the planets it supplies, right? So when does it take more energy to send energy to worlds, than you can actually send? Ugh, brain lock!!)
If that's the case, then the Negative Zone would eventually be destroyed (along with Reed Richards' brilliant prison). Actually, since they have portals to the Negative Zone on Earth, would the energy from the Crunch flow through the portal and destroy Earth as well?
But, here's the other side of my insanity: Could the Negative Zone be expanding somewhere as well? Perhaps not into the 616 (six hundred and sixteen) universe, but into another realm? Or does the Crunch not destroy things on the Negative Zone side, rather the two universe mingle, and things are exchanged? Maybe the Marvel Universe could one day engulf the Negative Zone, and they'd become one in the same. That would be weird, especially, if things tried to inhabit the same place at the same time, all kinds of crazy concoctions. I can see the prison winding up in Kree space, the criminals escaping, and Ronan being none too pleased that he has to waste time executing Earth's crap villains.
Thanks for indulging this lunacy. It's really frightening what happens to your brain when you find little better to do than watch various horrible movies all day. Both Under Sieges, and Day After Tomorrow. I think 30% of my brain decayed.