I vote just leave and lock the gate. The wraith probably would NOT follow us back. They seem more than content to just stay where they are and feed the way they have been for thousands of years.
Particularly if Earth (and our allies in the Milky Way) is prepared for the threat and fights back hard. The Pegasans are so technologically backwards that it would be simple for the Milky Way to be the much tougher dinner. The Wraith will stick with the easy dinner.
Another option that I really should have listed but didn't think of is the long-term strategy. Assume that if the Wraith are left alone, there is some possibility they will either eat up all the Pegasus humans or increase in numbers enough that they need new feeding grounds.
If this happens, any strategy other than eventual genocide (whether through some technological DNA fix or just a good ole fashioned bullet between the eyes) is self-defeating, in the long run. But since we have time on our side, we could put out feelers to Pegasus to establish solid alliances aimed at eventually throwing our firepower in to the fight against the Wraith.
What we don't do is tip our hand early by stopping cullings or fighting the Wraith willy-nilly. A good strategy would be to hook up with the largest power - say, the Genii - and start funnelling weapons to them to allow them to defend themselves. That has the advantage of locking in the genuine support of any power we hook up with - they see the advantage to themselves. It has the drawback of drawing attention from the Wraith, so a low-level armament program would be best; give the Genii only the level of firepower to help them improve their situation and cement their alliance but not enough to prompt the Wraith to try to wipe them out.
Then repeat this procedure throughout Pegasus, focusing on strategic allies (in terms of power, position and resources) and always testing them to ensure they won't double-cross us. The Genii might well get kicked out of the alliance along the way if they don't behave; but they could get another chance once they understand that they're only hurting themselves with their untrustworthy behavior. There will probably be many allies who will have to learn the hard way, but I'd say giving them one second chance to fall in line is reasonable. Make sure they understand there won't be a third.
The armament program will have to be disguised in some way, such as a new group of arms traders plying their wares. The Wraith must not be allowed to learn this is a coordinated strategy and very few Pegasus allies will be trustworthy enough to be let in on the whole story.
Once Earth has enough reasonably solid alliances in place, then it's time to pounce by sending large amounts of weaponry and spaceships, which Earth has been stockpiling for years or even decades. Then we take out the Wraith in one fell swoop.
In parallel, there will be Wraith DNA experimentation going on, just in case some other option can be developed that is not technically genocidal (though I tend to think of these solutions as genocide by another means). So it will be a race between Plan A and Plan B, to see who pans out first.
The Atlantis expedition doesn't need to be viewed as a failure. The strategy I outlined would be possible only because Atlantis has learned some valuable things, such as: you can't trust Pegasus allies; there are ways to alter Wraith DNA to change their feeding habits (unsuccessful so far, but it's a start); the Wraith target and destroy any powers capable of challenging them; and the Wraith are prone to internal divisions. All great intel that can be used to finally shape a winning strategy against them.
stay and fight until they sue for peace.
This makes no sense. Why would the Wraith ever negotiate for peace unless they have some human population as a food supply? And if the Atlanteans are willing to allow the Wraith to have a human food supply, why are they trying to stop the Wraith?
I'm sure if they had the ability cows, pigs and chickens would do the same thing to us humans.
Fortuntely the pigs being the smart ones, they'll just take over and run the farm as a communist dictatorship in which all animals are equal but some are more equal than others.
