FUD Zilla reports AMD is working on a dual-core Ontario "Fusion" processor with a TDP of only 9W. The expected launch date is sometime in 2011.
This can give you quite a good idea that Ontario will most likely go after the Atom market and even less than 9W TDP would be possible, but in that case you will have to turn ATI graphics off.
Ontario should come in dual and single core iteration and there will also be an embedded version of the chip. These TDP values are great for a dual-core Fusion as they are touching Atom N550 dual-core 1.5GHz TDPs. This particular Intel’s Atom have 8.5W TDP while AMD’s Ontario is supposed to have 9W with obviously better graphics inside.