Why would they go out of business? They have the equipment already, and remember most people who run these big operations are most likely doing it from a place where cheap electricity is available, so even if they are breaking even after electricity, why would they sell?
I honestly just don't see difficulty dropping to a reasonable point ever...
I'm not so sure all the big mining operations have the benefit of cheap electricity. Im sure there's a lot of players out there that are operating on slim margins @ $13. And no matter whether electricity is cheap or not, you still need to turn a profit to make mining worthwhile.
With regards difficulty - granted I don't suspect it will drop too much (if at all) but it could put the brakes on it a bit.