A couple of hints that the sale date will not happen is if the auction amount is your loan amount (including fees) and not reflective of the market, or if no amount is set for the auction. The only one who can postpone the date is the investor. In most cases, you need to specifically ask the loss mitigation specialist you're speaking to, to request postponement of the sale date. There is no guarantee but it happens more often than you might think.
Good luck to you on your short sale.
There are so many options available to distressed homeowners to resolve the circumstances rather than 'walk away' by letting it go to foreclosure. Yes, there are rare circumstances where foreclosure is the only option. But more often, even at this late stage, you can show more responsibility by participating in another option - including the short sale of your home.
A foreclosure hurts YOU the worst, but it also hurts the neighborhood, and all of us taxpayers who are subsidizing the foreclosure losses. Vacancy in a neighborhood hurts all of the surrounding property values. Vacant homes promote crime and vandalism. So I strongly encourage you to find another option if possible, or hand the keys over as soon as you're contacted. It's the right thing to do.