...But If I Were To Publish a Megadungeon
Online: I would create a separate site and just post it all there. Castle Triskelion is a good example of an online dungeon that is actively being published. The beauty of an online dungeon is that I can add and modify as needed, but I could see where it would get complicated to maintain and use as it grew.
Serial Print: John Stater's (The Land of NOD) NOD series is a favorite of mine and I personally think it would be a better way to publish a dungeon. So far there are 22 issues of NOD available on Lulu. The reality is that many of the current published megadungeons are in serial format, as we are waiting on the lower levels to be published.
The bigger challenge is on the part of the creator, actually finishing it or finishing enough of it so that the megadungeon is actually "mega." I have been steadfast in my refusal to plan to publish the Montporte Dungeon, despite the urging of the Monday Night Gaming Group and even my wife (World So Sweet). For now, I want to focus on playing in the dungeon, as opposed to publishing it.