Lots of issues with that concept. For one you'd probably lose the integrated Bluetooth headset/pointer at some point, leaving your phone with a nice gaping hole.
With the phone sitting on a table, there's just no way that having projectors project a keyboard would make for a comfortable working position without a stand. Even if the back of the phone is thicker at the top, there would still be too little angle towards you on the device for comfortably working when sitting down. You'd be staring at the table at almost a 90 degree angle and that's not good for your neck.
I don't know about you, but I certainly don't want to deal with a pointer on a mobile device. So having a virtual trackpad is not a plus for a device this size.