I bet Airbus is pissed. Skybus had placed orders for 65 aircraft. Of course, if Airbus really expected them to be in business long enough to take delivery, they must have been a bit loco.
Considering the backlog of A320 series aircraft, the Skybus slots on the production line can be quite valuable. Given enough advance notification, Airbus could change those aircraft to any of the A320 series - not just the A319. Airbus will laugh all the way to the bank just as Boeing did when the original launch customer for the 787 (Primaris) cancelled its order. By that time Boeing was on a roll selling hundreds of 787's with a 5 or 6 year backlog once production would start. The 20 slots freed up became available for earlier deliveries for airlines that hadn't yet ordered the 787 or more early deliveries for existing 787 customers.