This is what Gateworld.net had to say on this....spoilers ahead...
Mallozzi talks Season Eight changes
AUGUST 1, 2003
Co-executive producer Joseph Mallozzi has provided viewers with the first concrete information about Stargate SG-1's upcoming eighth season. In an interview at the Anime Evolution convention in Vancouver, Mallozzi hinted at Colonel O'Neill's possible promotion, and the introduction of a dangerous new enemy. Beware of spoilers below!
The conclusion to Season Seven will largely tie up storylines from the last few years of the show, including Anubis, the Ancients, and the Lost City. When the team returns next summer for Season Eight, Colonel O'Neill just might receive a promotion -- though that remains as yet undecided by the writers.
"That was a possibilty that we had discussed," Mallozzi said. "The fact that [Richard Dean Anderson] is not as available as he was in previous seasons -- he's only available for three days out of the week -- it would be easier to make him a less active member of the team. That said, a lot of people have been speculating that he might become a general, and General Hammond is going to ride off into the sunset. From a personal standpoint, I'm a very good friend of Don [S. Davis, who portrays Hammond]. I would be very sad to see him go. That would really be a last resort, if there's no other way. I think Don brings so much to the show, that right now I don't think anyone would consider anything like that."
If O'Neill may or may not be promoted, and Hammond may or may not exit the series, what do the writers know for sure about next season?
"For Season Eight, look for the introduction of a new villain to take over from the System Lords," Mallozzi said, and added that the team's new foe will not be a Goa'uld. "The Goa'uld will be around ... but let's just say that their power is waning. Over the course of Season Eight and particularly the spin-off, [the S.G.C.] will be facing a dire new threat."
The spin-off is Stargate Atlantis, which The Sci-Fi Channel plans to premiere next summer. Co-creator Brad Wright has promised a new villain to replace the Goa'uld for Atlantis -- villains who will apparently now be introduced in SG-1 Season Eight.
"Hopefully, we'll not only be working on Season Eight next year, but on the spinoff as well," Mallozzi said. "We're still awaiting official word on that."