I understand one of the key features is a bi-directional taxiway between piers, one on which you can make a U-turn at the bottom of the alley. It looks to me like the Kilos are going further from terminal 4 to accomplish this. So... if you were to have a pier where 3 now stands, and it was shifted SW to accomodate the taxiways, the NW corner of that pier would interfere with 2. I'm sure they could redesign 2 and 3 in such a way as to maximize space available, and not end up with a big parking lot, but I guess the costs would probably double.

I hear that 2 is not getting a face-lift, which leads me to suspect (no rumors: just a guess) there is a follow-on phase to this project that would build something on top of 2 and 3. Maybe even 1. I would also suspect there isn't funding or appetite for any of that, right now.