As cool as this would (or indeed SHOULD) be, there are so many logistical hurdles to get through that somehow you just know Sony are going to screw up something along the way.
For this to work, Sony will have to match Apple point for point on DRM. Songs downloaded from iTMS can be burned several times, shared across a limited amount of computers, and played on both computers and iPods.
So if I download a movie from Sony, I want the option to burn it to a DVD in addition to it playing in my PSP. The resolution differences are Sony's problem.