The lingering recession and rising game development costs are partially to blame for the lack of new machines. As game systems have matured, the cost of making triple-A games has soared. Tent pole titles now cost (on average) between $20 million and $40 million -- and there are some extreme examples, like Rockstar Games' blockbusters "Red Dead Redemption" and "GTA IV," that have reportedly sailed past the $100 million mark.
Next-gen games will cost even more. With publishers struggling to achieve a profit in the current economy, no one is in a hurry to add to their expense sheet.
Console manufacturers are no different.