I personally don't feel in the need of a new console generation, but I can tell they at times, especially the 360 struggles with certain games. (not to mention all the games that comes out on several discs, and in some cases in addition to that down scaled from HD.) I'm not at all saying the PS3 don't, but let's face it; it's a year younger, and a year further developed in terms of components than the 360.
These small issues aside, new consoles don't yet feel like a necessity. The technological advances is not by any means a large factor to my criticism and ruined experiences of today's games, and there is a lot developers should consider above it.
Nevertheless when a new generation is set on the calendar, I will probably set of the necessary money to get one (probably the Playstation, as it being the most suitable for me).