I think it would have to go somewhere different.
SG-1 finally ended (with the second straight to DVD film Continuum) with the extraction of the last Ba'al symbiote and the last remaining System Lord. The Asgard are now gone (with the destruction of Orilla in the last episode Unending), and IMO they have done the mythology aspect of the show to death. I'm not sure how many more of the ancient gods they can bring in without it seeming clichéd (even the introduction of Amaterasu and Camulus was pushing it).
Atlantis returned to Earth and Stargate:Universe was cancelled after only 2 seasons (and ended on a cliffhanger).
There was supposed to be a third SG1 film that never happened, and plans were in place for Atlantis and Universe films (also shelved). There was even talk of several crossover films that never got out of preplanning.