In deciding not to use the 3 cylinder turbo, Honda may be reacting to the new real world emissions testing regime in Europe. Re styling, the back view is a distinct improvement in my view. I've never understood the need for the large vent in the rear bumper of the present model.
For me, an attraction of the smaller engine is that it will warm up faster. My HR-V seems to take at least 5 miles (more in winter) for the instantaneous mpg to get where it shoud be. Will any of the new tests replicate the cold engine, cold weather, short journey condition? This could provide manufacturers motivation to improve engine warm-up (thermostatic louvres in front of the radiator to minimise cold air entering the engine compartment is probably the easiest).
I agree that those "vents" on the back of the Mk 3 are ugly. They are actually solid and serve no function. I would stick some extra reflectors there.