I'm hopeful that as time goes by details of why they're leaving the show will surface, but for now they wrote a very polite open letter announcing their decision.
Here are a few short quotes from the letter (for the full thing you can check out the source link at the end of this post.):
"As the creators of 'Smallville' we look back at 7 amazing years. We look back at 152 episodes. We look back knowing that the show will continue into Season 8 without us. After much heartache and debate we have decided it is time for us to move on."
"We are incredibly proud of our work on this show. We achieved what we set out to do. We never compromised our vision. We leave knowing that 'Smallville' is the longest-running comic book based series of all-time."
I find this very interesting.
Back in August of last year, Al Gough indicated very strongly that he wanted an 8th season of Smallville:
"We would all very much like a season 8, and that in our minds, would be the last season. But that will depend on many factors, not the least of which is ratings, so PLEASE KEEP WATCHING!"
That doesn't sound like a guy who thinks the show is done.
In October '07 Gough still sounded like they were on board, and re-iterated that Clark would still not be flying in season 7.
Then came February and what I thought was the most terrible episode of Smallville I'd ever had the displeasure of sitting through. It was followed by another awful one the following week, but I'll admit that after that the show did improve again.
Finally, last month CW confirmed that there would be an 8th season of Smallville. At this point it already seemed that the show was sliding in quality and I thought that they should let it end while it still had some shred of "good" left in it.
So... the question is: Has the show been getting worse because of Gough and Millar or in spite of their efforts to keep it at a higher quality level? My opinion? I think it's the latter.
The evidence that will reveal which of those theories is correct will be apparent in the quality (or lack of it) next season. I'm guessing that the network might have put pressure on them to make the show more "dramatic" by making the plots and relationships more outlandish, and that they balked at this. Also with one of the best things about the show not being there next year: Lex Luthor - it could have been a factor as well.
On the other hand I could be totally out to lunch and they just want to go make big budget movies. I guess we'll find out eventually.
What do you think is the story behind this and do you think the show will suffer for it?