I saw a clip for next season's Atlantis and it looks like Carter is moving there to be part of that team.
Teal'c aged 50 years in the finale so he's probably about ready to find a nice quiet planet to settle down on.
Jackson can't be a regular on Atlantis for some reason having to do with licensing and intelectual property. O'Neill and Jackson being characters in the original movie can't appear in more than guest roles in any spinoff series.
Mitchell and Shepard are both O'Neill clones and so cannot exist on screen at the same time without mutually self-destructing.
