MS, Nintendo, Sony.
I think that Sony prices themselves out of 1st place. Sure the hardcore gamers will pay for it. But If I am a soccer mom who knows nothing, I'd pick-up a 360 (which has been out for a year for name recognition), or a Wii (based on price point).
Maybe I'm wrong, but at $200-300, a poor person (USA poor), could afford a PS2, but at $500-600 they will go somewhere else.
I think that the Wii is going to be huge. Look how well the DS has done. It has wide appeal, is easy to use, and casual gamers can afford it. Talk about backwards compatibility, the Wii is going to be like a MAME machine.
On the downside, if I am wrong and people are willing to shell out $500-600 for a PS3, we are likely never to see a new generation maching under that price again.