Those runways still serve a ton of 737/A320 flights that have plenty of room to be upgauged to widebodies, and most of those runways could increase capacity fur

Those runways still serve a ton of 737/A320 flights that have plenty of room to be upgauged to widebodies, and most of those runways could increase capacity further still if FAA/ICAO decide newer tech can safely reduce IFR separation. Even with runway congestion, a big problem with an A380 successor is that any new commercial jet needs the fuel economy of two engines to have a chance of selling enough to be worth developing. Which in turn means that an A380-sized twin engine plane needs engines with ~50% more thrust than the current world record from a GE9X, which is already approaching material limits... A new 747-like plane with a partial double deck might eventually make business sense to develop within our lifetimes... But I think a blended wing (lol) is more likely than ever seeing another full double decker like the A380.