Not sure if this is correct or not but the blog thislalife.com (thanks Barbara Davies for the link)has speculated that the prequel will be called Spartacus: Gods of the Arena and also has the news about the new character called Gannicus (see yesterday's Spartacus Casting Call Gannicus will be in the prequel and for season 2).
The blog states that Gannicus will be the focal point of the series although the official press release regarding the prequel said:
Lucy Lawless and John Hannah take center stage in this story of the rise of the House of Batiatus and its champions before Spartacus arrives as a captured Thracian slave. Read full press release
For more news about the prequel visit AUSXIP House of Batiatus - the Spartacus prequel subsite
For more news on Season 2 visit the AUSXIP Spartacus Season 2 News page