Raph Koster certainly thinks so. He feels that single-player gaming is a phase we all went through, and that online, interconnected gaming is simply the next evolutionary step -- or, possibly, a return to form.
So how does this affect the MMO experience? With a sophisticated enough platform, there's no reason to think that a fully-immersive single-player experience couldn't exist cheek-by-jowl with an MMO experience. People talk about soloing, but that's just a concession, a way around the issue. What if, for example, while playing Bioshock, you arrived at endgame and left Rapture, only to discover a world filled with other players who've gone through the same experience? Is the future of gaming synthesis, rather than exchanging one form of gameplay for another?