See?! This is what the Puritanical demonization of masturbation has led to. (jkjk)
On-topic: Much like EQ, WoW will one day cede its throne to either one or multiple successors that revolutionize the MMORPG industry the way WoW did and continues to try to. It will eventually dwindle to a dedicated core of fans and hop-in-hop-out casuals, if only due to attachment to the time invested into their characters and the game as a whole, and if the day comes where WoW transitions to a free-play business model, that might inject some new life into it like free-play Steam releases tend to do for older MMORPGs.
That's just the nature of the beast in the game industry. No king rules forever, and WoW's had and continues to have an impressive run that crushed any expectations Blizz or the industry at large had on the outset. I highly doubt a day will come where the WoW servers are permanently shut down any more than the EQ servers; it's simply had too much of an impact on the gaming industry as a whole and spent too much time as a household name that there won't be a dedicated core audience and curious newcomers checking out the old relic years down the road.