[nzimmermann86]

It totally depends on the implementors, if no one implements it, it won't come. If nobody does the first implementation, no other vendor will follow - it's as easy as this.

For WebKit/SVG, features as z-index are easy to implement in the layer based SVG engine - it's currently disabled, but only because it's lacking dedicated tests: I'd still need to write new reftests covering that.