Google trends is useful and accurate, but must be taken within reason and context. I use it all the time, but you need to know how. For example, XBox360 got many more searches than Wii and PS3, but less sales thn Wii and only slightly more than PS3. Part of the issue may be that XBox targets the english-speaking western demographic that Google dominates, but there are many factors.
If you want to use this accurately, what you would do is first set a baseline. Look at searches for 360, Wii and PS3. Link that with their associated sales. Then compare that with searches for the new systems, and set a proportionate increase/decrease for the next gen. This would not be fool proof at all, but it could give you an indicator of where things may be going. I think it's skewed a bit to the "educated buyer", the one that does a lot of research. But it would be interesting.
