Some buyer's and Agent belived since the Short Sale is apporved you can close within 30 days or 45 days or because is a cash offer the bank will take less money because is cash.
well this is how it works, Everything start between all parties to be under contract subject to Short Sale approval. Buyer is willing to wait xxx amount of days if they want the property.
The bank will approved the Short Sale between those parties in the original contract if it take 30,90,180 days the Bank will only approved Mr & Ms on the original contract if there is a change in the contract it may not take that long it just required a new approval from all parties, Insurance companies if there is any and or investor depends on the case.
What I can say all banks are more effective doing short sale on this day so will probably take few day or couple weeks to get approved, But if that the house you want and there is nothing else similar you should wait for a couple months and see what happends.
I whish you good luck,.