The CW has already ordered a tenth season of the show, but who knows what could happen if the sub-par ratings continue. The quality of the episodes is higher than it has been for the past, say, two seasons, so what's the problem? Why have things gone so wrong when they started out so right?
Smallville's hardcore viewers are some of the most avid fans of any TV show. I have no doubt that they followed the show from Thursday to Friday without question (other than “why Friday? Is it getting canceled?”) But keep in mind that Smallville is on the CW, a network for people who...aren't old. Friday night at 8 o'clock is prefunk time on college campuses and it's also right about the time when teenagers sneak the family station wagon out of the garage to go shoulder tap outside liquor stores. People in Smallville's age demographic simply have stuff to do on Friday nights.
Once the mid-season break hit, even the most loyal Smallville fans got in the habit of living their lives on Friday nights, so when Clark Kent returned, everyone had already went drinking without him.
I'm torn. I don't want the show to continue for so long that it becomes complete garbage, which some argue it already has (F them), but I also want Smallville to come to a full conclusion, a satisfying series finale.
If the quality of the episodes holds up, maybe Smallville will be able to limp through the ratings long enough to make it to the end of a tenth season, where Clark can fly off into the distance, allowing the show's loyal and weary fan base to finally exhale.