When Intel developed its Nehalem-based chips, it severed a longstanding license agreement with Nvidia. The architecture (and subsequent advancements) utilize an embedded memory controller. Intel claims these types of chips aren't included in the agreement, effectively preventing Nvidia from making northbridges that interface with Intel's latest platforms.
However, the DigiTimes report claims that "Nvidia is developing the new chipset to bypass Intel's new Sandy Bridge architecture." What's more, with the recent investigations by the US FTC and suits for unfair business practices, it would be unwise for chipzilla to do anything that could be seen as anti-competitive.