I was looking around and I found an image format called SVG. from what I understand, it scales really well with any resolution. What's your opinion about it? and why isn't it replacing PNG as a file format?
Well PNG is for compressed raster/bitmapped images (i.e. a fixed resolution). I don't know much about SVG but from a cursory look, it seems to be a vector graphics format, where shapes are described with curves and such. PNG and SVG are really very different. You wouldn't want to save your raster images as SVG, as much would be lost in the translation (I'm not even sure if SVG can do raster images). Likewise you wouldn't want to save vector based art in PNG format as that would lose all the scalability.
There is software that can convert from a raster format like PNG to SVG, but I wouldn't expect the results to be very good for detailed images like what you are trying to scale.