TUAW believes that the upcoming MacBooks will indeed be powered by NVIDIA chipsets and will be delivered on October 14th.
A source tells us that Nvidia is showing off new MacBooks to their employees, and word is going around that the new versions will be released as soon as October 14th.
Apple was first rumored in July to be incorporating alternative chipsets in future laptops. While Apple would still be using Intel CPUs to power their laptops, the support chips (including graphics) were said to be supplied by a company other than Intel. NVIDIA topped some lists as the most likely supplier. A subsequent report pointed specifically to the use of the MCP7A-U chipset in future MacBooks. This NVIDIA chipset was briefly detailed by Expreview:
MCP7A-U is the top class chipset in the MCP7A family. Though it could be named as GeForce 9XXX, it will be come the first mainstream uATX mobo with DDR3-1333 support. Sources inform us the MCP7A-U will be the fastest mGPU, but who knows.
Such a move would address user complaints about the use of Intel's slower integrated graphics chipsets in current MacBooks. The move would also prepare Apple's laptops for the release of Mac OS X Snow Leopard which will allow applications to utilize the more powerful graphics processing units.
MacRumors has also heard similar whispers which lead us to believe these reports could be true.