Does Svg Support Transparency. Format is highly compressible and lightweight. It does support alpha transparency not limited to the matte color indexed transparency through the Save For Web dialogue.
If possible avoid creating artwork that will be rasterized in the SVG file. If you want rescaling without losing quality for computer graphics not photographs then you need a vector format such as SVG. For vector graphics this may not strictly be seen as transparency but it requires much of the same careful programming as transparency in raster formats.
The SVG specification is an open standard developed by the World Wide Web Consortium W3C since 1999.
BTW its the same reason why Inkscape does not support multi-page documents. Ive been importing these images into Unity game engine which recently began supporting SVGs. If possible avoid creating artwork that will be rasterized in the SVG file. There is a workaround to this.