i'm going to go the complete opposite direction. don't get me wrong - personally i think 3D is the most amazing thing ever but i've been watching the news reports and box office numbers and things don't look so good for 3D. consumer interest seems to be wanning.
3DS will probably be successful but imo it will be successful despite 3D not because of it. i'm not sure what sony should go for but trying out some sort of alternative tech is probably a good idea. maybe it's just me but i would be interested in a tablet style of device.
I would say the reason they don't look good is because consumers are sick of paying ridiculous prices for 3D movies even when they already own dozens of pairs of 3d glasses.
If 3D movies were same price (no reason why they shouldn't be), if you brought your own glasses, things would be looking better.
The difference between 3DS, 3D movies, and 3DTV is that more than likely, the 3Ds will be reasonably priced.