Runway length is just one of the A-380 issues, and, assuming you have room to lengthen (not the case at every field), it is one of the simpler ones (though not an inexpensive one).

Some of the bigger challenges that need to be tackled are gate spacing, sufficient number of jetways, ability to handle much larger groups of people in the terminal at a given gate area and much greater amounts of cargo, deliver more fuel, etc.

Sufficiently wide taxi-ways are also critical, and often not easily adjusted after an airport was designed. (Witness the AF JFK incident.)

As a private for profit airport owner (through our fund), it is certainly important to get as many carriers as you can to your field. Doing it in a profitable manner is even more important...all the capex required on the hope of KE running a periodic service isn't a trade we would make. We had commitments from several carriers before we launched the capex project...and split the bill with the carriers. Airport management may have other firm commitments...but one a day from icn isn't compelling unto itself to do the all the work required.

I recall the 9/27 project was needed also to better facilitate 747s in warmer weather....so the runway portion of the work covers multiple objectives.

Finally, its worth highlighting that while Atlanta is a very busy airport, its econmic value is questionable and may be negligible to a profit motivated investor...due to the high percentage of non-O&D traffic.