I agree that svg is not dying, it's still growing.
Using a byte encoding for element types and numeric values over strings would likely dramatically reduce sizes. For example:
<z:rect x="0" y="0" width="10" height="10"/>
Could be binary encoded as something like:
00 00000000 00000000 00000110 00000110
(shape, x, y, width, height)
Total size of compress XML is probably 30-40 bytes. Final binary size is 16-18 bytes.