Problem is, you're not taking the increased development time & costs into account. As you mentioned, Sony is barely profitable as of now, and I don't think they could afford launching a new system until they get enough cash out of the PS3.
Move and stereoscopic 3D sure are gimmicks, but they will still help in making the PS3 look fresh. A lot of developers are still busy working on their first or second PS3 title (Team ICO and Polyphony Digital have yet to release anything major); apart from maybe Naughty Dog and Liverpool Studio, I don't see who at Sony would have the resources to even start working on a PS4 demo.
I agree that we should see new machines in 2012, but my guess is that Sony is going to wait as much as possible before making any announcement.
