From Joseph Mallozzi's blog update for July 15, 2010:
(Please follow the link for the complete blog update.)
July 15, 2010: Atlantis crossover? Which begs all sorts of questions! And another BIG guest blogger announcement!
With word from producer John G. Lenic that the deals have been closed on those Atlantis alums, we can now move forward on the script, secure in the knowledge that both extra-special guest stars will actually be on hand to say the dialogue written for specifically for them. Great news for fans of the old series. There was a reluctance to move ahead with an SGA crossover, particularly on my part, because the feeling was it would step on the timing of the SGA movie, Stargate: Extinction, the events of which directly proceed the Atlantis series finale, Enemy at the Gate. But given the delay on the movie front and the ideal premise pitched out by Remi Aubuchon and Brad Wright, it was decided to go ahead with the crossover. Not a big deal, but it will require some changes to the Stargate: Extinction timeline which, in turn, will beg a host of questions, some of which will be answered in episode #15, some of which won’t…at least not right away:
... Hey, I just noticed that even though I mentioned the deals had been closed, I didn’t reveal which characters would be putting in an appearance.
That’s because SyFy will be making the grand announcement when the time comes. Watch for it!