I recently saw how tiny the new Eye really is ... it's much, much smaller than I've thought, and especially thinner. I mean, 186mm X 27mm X 27mm ... that's a really thin bit of kit, and certainly makes it easier to pack in with a game, and make it likely to become relatively low-cost soon(ish).
If Sony or someone else manages to find a good gameplay possibility, they can still convince people to buy it, and depending on how things go, they can still start shipping it with the box at a later date. It's all up to Sony to decide how they feel about the device in the future, and how clever they are with their SDKs - e.g. in the UI video, you actually see a user type some text using the DS4 as a pointer, which may or may not require the PS Eye 2.0 tracking the device (the gyro being sensitive enough, this isn't actually necessary - many Move pointer interfaces in games also just used the gyro for controlling a cursor)
Conversely, having Kinect 2.0 as a pack in with the Xbox One doesn't also guarantee success. But it is providing such a tight user interface integration for it that it makes a lot of sense to include it, whereas for the PS Eye 2.0 I am not yet convinced it will be as suitable or necessary as a UI enhancement - the basic features of the DS4 are so expansive that it has enough interfaces by itself, and the PS Eye 2.0 is far less likely to be a reliable input device all on its own than Kinect 2.0 is.
Like Shifty says though, let's wait and see for the companies to provide some actual games that make you want to own it.
The new PS eye was a tick box that Sony thought required ticking. It's done that, but no matter what it's a dead bit of kit.