Not easily. You can use matplotlib to do it directly (basically,
duplicate what is done in the .save() method, but save to a
StringIO.StringIO() object). I have some patches up at the Sage cell
server. If you apply the hunk at
https://github.com/sagemath/sagecell/blob/master/sage-patches/02-sage-show.patch#L189,
you should be able to do something like:
sage: import StringIO
sage: f=StringIO.StringIO()
sage: a=plot(x^2)
sage: a.save(f,format='svg')
sage: f.getvalue() # gets the SVG string
Thanks,
Jason