Hi i think they are wrong. I think there will be no flights for 2 days and all airlines would move to the new IST Hong Kong style.
maybe BA just didn’t bother updating systems?
i mean the new Airport will take over the code of IST anyway!
Dont know what what the new airport will be called of course !
i am 99% sure you will fly to the new IST and we are expecting a nice review from you !