If you are, then you should probably speak up. The network ordered 13 episodes, but has not made any commitment beyond that. Normally, for a strong show the network would kick in at this point and order another 13. But they have not. The ratings were good enough to not immediately cancel but not so good to open up a commitment.
So go to your twitter page and #saveconstantine and put in your two cents. Daniele Cerone, the title character in the show, is leading the charge.
If twitter had existed during the age of Firefly, what could have happened?