This is going off the testament of a single man on the internet, so it's far from confirmed, but it's convincing enough to warrant a closer look: seems Microsoft's long-rumoured "Opus" chipsets may have begun shipping. Featuring a 65nm CPU and 90nm GPU, it's believed the Opus is a stop-gap chipset, to be used in repaired/refurbished consoles (while the Valhalla chip is used in new consoles). The chip pictured comes from a repaired unit, so at least that part of the story checks out. What's this all mean? It means that, if true, when your 360 RRoDs and you get it repaired, when you get it back, it'll (hopefully) be a lot less likely to do it again.
The New Xbox 360 Opus Mainboard *Pic* [Xbox Underground]