According to Executive Producer Mark Verheidens’ blog:
Sci-Fi Channel has ordered 20 episodes of the BSG prequel, to start airing in early 2010. Plenty of lead time there! I wrote the first post-pilot episode a few months ago, so I am fairly familiar with the story and I’ll just say – if you enjoyed the challenging and intriguing world of Battlestar Galactica, you’ll love Caprica. That said, it’s as different from Battlestar’s “feel” as you can imagine, dealing with emotional and science-fiction conceits in an entirely different and very adult way…
And here’s the Variety story.