And thus the developers all yelled "No". 3D TPT will not happen in the next few years. To much coding and people would complain about complications for the computers.
Not to mention the EXTREME lag it would cause, just to have a few pix of depth would drop the FPS so far it would be unplayable. Computers are not near fast enough yet.
i was having a daydream about this, but i realized that all 3D games that you have to manually move around and place objects have had a horrible UI, what may be possible with lots better technology, is some sort of swivelable-touch-screen cube that you could zoom into and have TPT run on (if all that makes sense) but thats obviously in the far future... wow my daydreams are lame :)
PT is 3D would require a ton of work, and in order to run the program, you would need a quad core or better.
Maybe in the future (a few years) somebody will take the electronic aspect of PT and make it into a 3D program, but adding all of the physics would just be to laggy.