My question is, will RDU
need to be converted for the A380 to land at if GSO
isn't suitable at the time?
can handle a 744 (which I believe they can), then they can handle the 380 in a diversion situation with almost no extra work needed, since the pavement loading is similar to a 744. It wouldn't be enough to handle them on a regular basis, but as long as it's diversions only, and as long as there's a remote stand to park them at where the wingspan won't block taxiways, minimal problems
It is true that just about any airport that can handle commercial jets will be able to handle an A380 diversion. You can always use airstairs on the tarmac to unload. It would not use much runway at all to take off if enough payload and fuel is offloaded, and landing distance is not nearly as much of a problem as takeoff distance for most airliners.
And you are right that the ability to handle a diversion does not neccesarily mean the ability to handle regular flights. You could land a 747 at Midway or at SPI
in an emergency, and you could even take off again. But payload restrictions and gate restrictions would stop any attempt to have regular service.