GIF this days is almost always used as a moving-picture format, which is not something standard PNG does. The number of actual GIFs being passed around these days that would be better off as PNGs is virtually zero.
That's kind of my point. Animated pngs support 24bit color and transparency--which gifs do not. The carrot of transparency and more colors weren't enough to replace gif. It looked like the lzw patent scare would be enough but since that expired in 2003 nobody has been motivated to fully implement the spec or create content exclusively as pngs