Despite the media coverage and thousands of fans who threw their support behind the show, ratings for the series in it's abbreviated second season just weren't enough to keep the show afloat. Although if you look at the show's viewership across a variety of channels is doing pretty well, the advertising money is all about how many people tune in to watch on television only.
Sure, there's always the threadbare possibility that Jericho could be picked up by a cable network, but it's anyone's guess and up to the good graces of some forward-looking network exec whether it will happen.
Although not visual effects heavy in a sci-fi sort of way, I imagine the series is not the cheapest to produce with it's use of military vehicles, battles and other scenarios. If some cable network didn't pick up Journeyman, which no doubt could be produced much more cheaply, I don't see them picking this up.
I don't know how the heck they're going to wrap this up in a one hour episode, BTW - it's going to take some fancy writing to do that.
The series finale of Jericho will air on Tuesday, March 25th.