Well the more interesting part of this news is the timing (if true obviously). This is a bad bad news for Sony imho. They are likely to suffer a lot more than Ms from this launch: they have a lot to lose in Japan, they can't price their system as low as Ms will to somehow resist the storm till their respective next-gen systems are out.
The timing is what I find hard to believe. I can believe there are dev kits out, they are usually out about two years ahead of launch to some selected developers, but 2010 sounds early. The Wii is still selling extremely well compared to competetion and a new console is often introduced about two years or later after the previous one has peaked.
Would a 2010 launch be bad for Sony and MS? I think that very much depends on the price and game line-up. I think a 2011 launch may be just as bad if that gives Nintendo time to get some really compelling games ready for launch and good third party support as well.
Whatever hardware (handheld etc.) Nintendo have cooking at the moment, I hope we will get to know more from GDC.