Flat graphics are actually extremely compressible with PNG's.

That's actually one of the positives from moving away from gradients and shadows everywhere, funnily enough.

They are, but as soon as ther is anything that is not a rectangular gradient with a continuous delta, they're probably still bigger than SVGs

Unless your graphic designer provides you with vector graphics embedding a vector for each pixel of the rasterised image of the original vector graphic.

Sigh...

That's almost as bad as the autogenerated SVG I once was sent that used hundreds of thousands of think horizontal lines to fill an area. Instead of, you know, a filled polygon.

The sheer number of vectors could make any renderer I threw at it crash.