Battlestar Galactica: The Complete Series will be available as a Blu-ray box set on July 28, 2009 for $350 suggested retail ($209 preorder price from Amazon.com). The 20-disc box set will include all 4.5 seasons of Battlestar but unfortunately leaves out the 10 webisodes that were included on the DVD version.
Blu-ray Review has a good breakdown of the set’s extras.