All orders will survive the fork, but after the fork they will execute relative to price feeds rather than the average.
So I assume you're referring only to margin call orders.
What if the BitUSD price is going up (that is, the real price, determined by what people are willing to trade at) -- but that is not reflected in the feed until some time later? I wonder if that delay might exceed the moving average delay long enough to increase the risk of getting into an FDIC situation, where some shorts' collateral is totally wiped out and they need to be "rescued". Did the BitFDIC idea ever make it into production, anyway? How does the BitFDIC deal with needing to print BTSX?
 I prefer avoiding the term "fork" or "hard fork" because that implies something awful. Another thread proposed "Mandatory upgrade" to be the terminology for any change to the blockchain validation algorithm.