According to this article over at HKEPC, the high-end motherboard market may well be seeing a significant shift following the launch of NVIDIA's new flagship 680i chipset last week. NVIDIA are apparently now keen on producing entire motherboards through OEM and reselling them to add-in partners, much the same as the way it's always worked with graphics cards.
Since the high-end market is less demanding but challenging to manufacturing technology, the high cost of development embarrasses some manufacturers to manufacture high-end products by itself. In the display market, both NVIDIA and ATI are manufacturing high-end display by itself through OEM and then resell the product to manufacturers such that they can sell the product under its brand. As this strategy is a success, NVIDIA plans to introduce it to the motherboard market.