I don't think any of these motion things are going to succeed. After all, many people who own a Wii already own some or other console to make up for some traditional gaming.
I see swarms of casual gamers and families going for Project NATAL, but after a month or so they'll be over it. The only thing that matters to Microsoft though is that it sold and that gets them a lot of money and statistics. There will obviously be less sales for the Move, but I must admit, I have a feeling that some titles might actually be non-casual and pretty good. While Microsoft is trying to blow everyone out the water, I think Sony is taking the tamer route by making up for whatever the Wii can't.