What are the reasons motion controls are coming to the PS3 and 360 with so much advance notice before the technology is ready for consumers?  Generally it's not good to let your competition know your plans, so I think it's main focus is to try to keep third party publishers.

They are letting people know so far in advance because they want third parties involved. They need time to make stuff.

Mainly I think for third parties, atleast the Sony wand; speaking of Natal I can see some MS studios developing interesting games just for Natal, but generally both the motion controles are built to attract third parties with Wii ports or so that they leave the Wii; this is also the main reason why I and many people think that out of the two Natal can be the better way to increase sales.

With Wii it was the same thing wasn't it? The motion controls where shown atleast 2 years before it was released. It's just normal business strategy. So i don't see the problem here?

it think is too late for hd motion controlls this gen....

It's an attempt to co-opt the values of the Wii. The target is both potential Wii consumers, and HD consumers that might be susceptible to switching over as Nintendo tries to move upmarket. Whether or not it succeeds will depend on execution, and especially software.