PVR feature in cocos2d is kind of for expert users, or at least for those who knows why it should be used. If your game is really texture intense, then PVR usage might have sense. PVR loading is handled by cocos2d itself from main bundle, not only because assets doesnt support it, the whole UIKit/CoreGraphics framework doesn't use it. SpriteKit doesn't support PVR neither.
PVR is a neat cocos2d advantage, but it is mostly useless for 95% games made with cocos2d. Most of people use .png for assets and feel themselves fine. Also, assets are optimized by Apple internally, they are compiled in somewhat with .kar extension and some people outthere found out that they show close to texture atlasses performance. I don't have any info about memory usage, but I think there are might be small optimizations too.
Ok so, PVR is not what we want to focus on, while it is well-supported by cocos2d, the primary way of loading assets will be to load .png. As soon as CB will implement assets generation, plain old asset loading will be gone from cocos2d forever (only PVR and texture atlasses will stay).
Also note that PVR compression can often show some artefacts in the result texture, especially with alpha chanel, so it takes considerable effort to fix them.