This is something I disagree with.You get to the 00s and MMOs are taking over D&D's territory in a lot of ways. I know WAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAY more people who play WoW then who actually play D&D. Almost every D&D player I know is involved in some sort of MMO, but the reverse definitely isn't true.
Imho, (normal*) MMOs offer a completely different experience from playing an actual tabletop RPG, and therefore don't and likely never will replace D&D. So, it's no wonder most MMO players aren't interested in playing a table-top RPG. The reason many D&D players have played or are still playing (Fantasy) MMOs is the similarity in theme. I played one myself a few years (Dark Age of Camelot), because I enjoyed that the setting and the creatures were based on real-life mythology. I didn't play it because I hoped it could scratch my RPG itch.
So, to me, saying "MMO's are going to take over from table-top RPGs" is like saying "Fantasy novels are going to take over from table-top RPGs". Just because (almost?) every D&D player enjoys reading Fantasy novels doesn't mean, reading them will ever replace playing an RPG for them.
* There's a few extremely niche text-based MUDs where actual roleplaying is taking place because it's obligatory.