title_body: How well is SVG (being a "pixel image" alternative) supported?
upvoted_answer: As Donald points out in his answer, (new) devices would have to support SVG 'images' as support for SVG is specified in the EPUB 3.0 standard.
  
  For line drawings, but also for zoomable images (maps come to mind), this is a vastly superior format over any pixel based file format.
  
  How soon that adaptation will happen will be influenced by how easy it is to adapt the various rendering engines used in the devices. Some of the features of 3.0 require more processing power, potentially reducing battery life even if not actively used. 
  
  Conversion to non-EPUB formats of EPUB 3.0 with SVG is going to be more difficult, some will not support it at all (which would require rendering in some pixel based format at some resolution), conversion to others formats (PDF) would become more complex than the current text and image conversion.