Emmerich can take his trilogy and shove it. Nothing against the man or his original trilogy idea, but there's no point to it now.
Once SG1 took off on Showtime, he said he'd given up on continuing the trilogy of movies.
Besides, the original movie didn't do all that well, and was so long ago, there'd be no point in trying to continue it.
Similarly, there's no point in either trying to continue any of the 3 SG shows in the theater, or adding something new to the franchise in the theater. It'll pretty much be another Firefly/Serenity. Only the fans will go see it because there's no way you can just bypass all that history and still have a film that makes sense for those who never watched the show. (Granted, with it's fanbase, it would probably have a more successful release than Serenity.)