We know Microsoft will eventually be releasing a new console, but at this point in time we can only speculate about its expected features. But the website Xbox Evolved claims to have insider knowledge of one feature that will make you hang onto some your 360 games for a long time.
According to their source, the third Xbox installment will be "Forward Compatible" which will provide graphical and performance updates to Xbox 360 titles. This ranges from increased draw distance, improved framerate, or perhaps even new DLC. This would be the equivalent of upgrading your PC video card to allow for higher graphical settings. This, of course, will only apply to games still in development for the 360.
Our sources indicate that Microsoft is in a stage of "testing the waters" before they nail down the final specs of the new machine. Introducing these options early on to developers means that the games they make for the Xbox 360 will have no life on the next platform, and allow them to begin much earlier in figuring out how the next Xbox works.
We think that's supposed to be "new life" not "no life," but anyway. It's entirely possible this could work, but I'm not sure how cost effective this would be both on the hardware or software side. For now, this is just a rumour, so don't get too excited.