As much as I hate Microsoft. I do believe they are in a position to do very well next gen. They have NA wrapped around their little finger and while Japan shuns the 360, NA is a much bigger market.
Nintendo has always been kind of unpredictable. Like you said nobody knows for sure how the Wii U will do. (I hope well)
Sony has come a really long way since it's PS3 launch. I think people are starting to realize that Sony offers a very healthy variety of games to the core gamer and I believe they will continue this trend for next gen as well.
Basically I'm hoping WiiU will do well, and even though 3rd party may jump on board, i'm guess the main driving force for Nintendo will be (as always) Nintendos 1st party games. I'm guessing/hoping the Nextbox will try to be more like the Wii was this gen and compete strictly for the casual market with kinect while alienating their hardcore fans, and I believe Sony will make the push with the "We cater to core gamers!" mentality. Possibly taking in those fans from Microsoft who don't like the path the Nextbox has taken.
Then again I could be dead wrong :p
