Hannerdyn
Explorer
Well let's see...
Gap between 1st and 2nd edition: 12 years (1977-89)
Gap between 2nd and 3rd edition: 11 years (1989-00)
Gap between 3rd and 4th edition: 6 years (2008-14)
I'm not a mathematician, but if the pattern holds then 6E would be out sometime between 2017-19, and 7E 2-3 years later.
At some point, perhaps editions will reach some kind of Kurzweilian critical mass and the Singularity Edition will haveth arrived.
Right, the edition that will have been written both before and after all infinite editions.