We've got an actual, official crossover this week; no theories, no conjecture, not wacko off-the-wall stunt like last week.
On Friday night, the 'Stargate SG-1' crew finally were able to visit their counterparts working the Atlantis stargate. (Daniels had tried several times in the past to dial up the Atlantis stargate's coordinates but had never been successful.)
Of course, 'Stargate SG-1' begat 'Stargate: Atlantis' as a spin-off, but they had crossovers afterwards; all involving someone from the Atlantis crew returning in some way to Stargate HQ back on this alt. TV Earth. This was the first time the original crew went over to the spin-off.
As seems to be the case with the crossovers, it mostly focused on Samantha Carter and Rodney McKay going the Marvel Team-up route. This time, they worked together to find a way to disable the Ori's "super-gate" to prevent their alien enemy from ever dialing new ships to attack Earth. (And to accomplish this, they wanted the super-gate to dial into a black hole found in the Pegasus Galaxy.)
Of course, as the TVSquad reviewer pointed out, this now give the wraiths of 'Stargate: Atlantis" the opportunity to make their way to Earth.
This is bad news for their world, but great news for Toobworld in general, as it can lead to more crossovers - even if it's only the enemy alien race of the wraiths which supplies the link.