The Chicago Tribune has an interesting article. It goes on to repeat the rumour from the NY Mag's Vulture Blog about a possible mini series to fill the gap left by the delayed Season 2. So far we haven't heard anything about a mini series from any official sources. Just speculation and alot of hope.
The Chicago Tribune has this interesting bit that doesn't really say yes or no to the mini series but it does give you a little hope:
Starz is considering a "Spartacus: Blood and Sand" prequel miniseries in order to have something "to fill their January hole."
A source close to the show who asked not to be identified said that a possible prequel miniseries was just one of "multiple scenarios" that are being considered. The prequel miniseries "may happen and may not," the source said. Nothing has been decided, the source noted.
That's not much to go on. It's an interesting rumour and for the moment, it remains a rumour.