There won't be two Spartacuses runnning in tandem. The new second series hasn't started recording yet and is set for broadcast at the end of this year or early next year. The prequel is on now and is only six episodes I think, so will end in February, and is designed to show what happens up to the start of season one.
They made the prequel to fill the gap so the original Spartacus could get better, unfortunately he hasn't.
They made the prequel to fill the gap so the original Spartacus could get better, unfortunately he hasn't.