I transit through HKIA every couple of months. Last year I purchased a 3GS at the SoundVision store at HKIA. The Invoice was a "Fortress Store" invoice, and at that time they sold the iPhone 3GS only as a store package with an extenal battery pack, car charger and screen protector to get some additional profit.

I was there two weeks ago and they were all out of 3GS Phones and had no iPhone 4's at all. There is no official Apple store at the airport or in Hong Kong (except the online version of the Apple store). But the store in the airport carries several Apple products such as Macs and iPods.

Once supplies catches up with demand, I suspect the iPhone 4 will be sold there (clearly they have a Fortress connection).