Ray,The BRZ addresses a tiny market, the folks that want the classic, Colin Chapman-style sports car...light, RWD, responsive. Folks that want it to be AWD have probably never driven one. The easy, controllable gymnastics that the car can do would likely be lost, and that's frankly a large part of its character. If you're busy comparing it to WRX's and STI's...you missed the point of the car.
All that said, it is indeed time for an update, and there is, of course, room for improvement. It doesn't "need" more power or a turbocharger to be a great enthusiast car...but...I miss FI. If Subaru came out with a successor with a nicely-implemented turbocharger on it, I'd probably start scheming how to buy it. Assuming they didn't flush the character of the car down the toilet with changes.
The last time I was at the track an instructor, competing in a Time Trial class, spun his BRZ. He went completely off track and into the grass / weeds. I mention this point to add a little perspective to my opinion that putting 50-75 more horsepower with the trickiness of turbo delivery (coming on boost changes the handling balance at the time of boost) might make the BRZ a real handful to drive. I think the car is setup with a slight over-steer balance to begin with. Adding a turbo might bring up far more interesting over-steer adventures.