I must say that I look forward to seeing what comes out of Will Wright's Spore. Of course there's the possibility that it'll fail completely; there are probably hundreds of factors that all need to function together for it to actually work and be playable. Considering how it's built up, how the player will be able to affect so much in development of the species they "create", it will probably involve an incredible amount of play-testing to work out all the bugs. And even then there's no guarantee that they've covered every possible scenario. In a more traditional game you'd have the testers go through every level multiple times, trying different things and seeing what breaks the game, but in a game as ambitious as Spore you'll have an almost unlimited number of scenarios and combinations of paths that the player can choose.
But even with the increased complexity, I do believe that this kind of game, the one that actively evolves around the player's actions, is the way forward. Today there's a long development time and a big budget associated with every big-hitting game, and an increasing amount of those are franchises like Halo, Half-Life, Final Fantasy and Grand Theft Auto. With the power and capacity of the next generation development won't be getting any easier either. Spore is taking a different path from the linear, big-budget games, one that I believe other developers could learn from.