Actually, that doesn't mean anything (yet).
There was a contract for 13 episodes.
The pilot was shot, but then Fox scrapped it. However, that counts as one of the 13 contracted episodes.
8 Episodes have shown, and there are 4 more scheduled (the final one scheduled is called "Omega"). The completes the entire order.
The "13th" episode being discussed was created but apparently wasn't included in the contract and Fox says they don't want to air it. It apparently isn't required for the overall story.
Fox isn't supposed to make a decision on the future of Dollhouse until late May.
http://www.nj.com/entertainment/tv/i..._in_limbo.html