Configuration files buried within some versions of Mac OS X show evidence that the next iMac and Mac Mini will indeed be based on the NVIDIA MCP79 chipset. Apple recently switched their MacBook, MacBook Pro and MacBook Air models to the NVIDIA chipsets in October. Amongst other benefits, the new notebooks have much improved graphics card capabilities, which make them more suitable to take advantage of OpenCL technologies coming in Snow Leopard.
Apple will apparently be bringing these improvements to both the new iMac and Mac mini. While many have expected the iMac to receive these upgrades, the fate of the Mac mini has been less certain.