That actually almost happened a couple of months ago when the government couldn't agree on a budget and threatened to shut down. The deadline was fast approaching and Pres. Obama said he would NOT approve anymore extensions. We were all preparing to NOT get paid for an undetermined amount of time until a budget was approved. Of course, all military members were expected to show up for duty as normal. The commissaries were going to shut down and all "non-essential" government employees would be laid off. Soldiers were told that they would eventually get back pay, but none of us were going to get paid at all until a budget was agreed upon.
Lots of panicking going on. I was FRG leader at the time and I had wives calling me freaked out because they live paycheck to paycheck, no savings, no preparations at all and had no idea how they were going to make rent, etc.. We were being told to warn people to prepare to not get paid, contact all creditors, where to apply for AER loans or rental/utility assistance through USACares..
Of course, at the very last minute, they all agreed on a budget and everyone ended up getting paid. Crisis averted. But it was an eye opening experience for many military members and their families!