Here's sci-fi's official announcement:
http://www.scifi.com/scifiwire/index.php?category=2&id=37607Ten seasons is amazingly long. Though I'm not sure what they mean by "record-breaking"... after all, Doctor Who was on for 26 consecutive seasons.
SG:Atlantis is still around, so I imagine they'll periodically have SG-1 regulars popping into SG:A somehow. Or maybe even have some of the more popular characters transfer over to the other show as permanent cast members. Like when the Klingon guy from ST:TNG showed up on ST
biggrin S9 and started making out with the tapeworm girl.