Stargate SG-1 has to come to a nice, defined end. One last movie with Jack O'niell and the rest of SG-1 to wrap up their story-lines as is needed. Perhaps a character or two could head over to Atlantis, but "SG-1" should reach a conclusion. Teal'c should either die or go off to lead his people. Daniel should end up with Vala, or go over to Atlantis, or both, but his time with SG-1 seems over. Jack and Sam should be together (the producers spent time building up the angst, and then have been mostly pretending that their feelings for one another don't exist) or... something. No idea with Cam. Never grew on me as a character, to be honest.
As for Atlantis...let's face it, the show is a mess. I would end it as soon as possible, with a conclusion so it can be put to rest along with the Stargate franchise.
Universe might be worth it in a few years, but a totally new writing staff will be required.