Tough call. I think that multiplayer games will certainly continue to be popular, but I think it is hard to predict whether they will dominate in 5 years. Single player games will always have their place. I personally spend much more time on single player games than multiplayer, but it depends on the game. I think a major factor in single player games remaining popular is the continued development of AI. For example, with Starcraft, the campaigns were great, but after a while, single player mode became way too easy, and I could beat 4 or even 5 computer opponents at a time because I knew exactly what they would do. Playing on BattleNet was a different story, though, because even a poor player could surprise me.

So, I guess my point is that they will both have their place in 5 years, but AI needs to be developed further (which I think it is) for single player games if they want to remain competitive. I also think it is important for games to support both. I don't see myself ever buying a multiplayer only game. On the flip side, adding multiplayer support to a single player game increases the longevity of the game.

Asking such a question is not analagous to having asked sixteen years ago whether text-based or graphical games will predominate; it's more analagous to asking whether PC or console games will dominate in the future. Text vs. graphics was an issue of how to relate the same experience in different media. PC vs. console is an issue of how to relate different experiences in different media. It's the same with multi-player games and single-player games.

Multi-player games may be similar to single-player games in construction, but true MMP games must have very different design goals. Death-matching in Quake is not the same as navigating the levels. There are different goals involved, and different experiences are created for the gamer.

Most gamers enjoy games for the interactive experiences and fantastic environments they create, not for the methods they apply or the principles they are based upon. If AIs are indistinguishable from real people, the player has no reason to complain; if they aren't, a multi-player solution might help. Such "integrated" games will probably become a lot more common, because graphics are improving with the accelerator market leaving a lot more room and demand for either more sophisticated AI or multi-player support in its place.

But a TRUE, non-hybrid multi-player game, one that Bob and Joe and Frank Q. Gamer would get together and play on a Saturday night, is a different story. Board games have utilized this model for decades, but it's gone relatively unexploited in the PC game industry. There are a whole new set of non-programmatic problems involving the control of people. The problems we face become less of the sort "the little guy can't walk through this door" and more like "get him off here, he keeps nuking everybody." How the genre will develop, I think only time can tell.

Poker and Solitaire both involve moving cards, but beyond that, they have very little in common...