I hardly wish to deflate your effort, but are you aware that Adult Swim's website offers a feature that allows the customer to design the content of a DVD?
I regret to say that I doubt the petition will create enough influence to deliver the latter seasons. However, if you don't mind a DVD with the episodes and no features, the custom DVD builder is available.
I am aware of the feature that Adult Swim offers. However, it is less the idea of being able to watch the episodes (I have them all on my computer) and more the idea that the show deserves its own DVD release like any other show.
Warner Bros. already released the first volume with special features and commentaries, so I just wish that they would complete what was started.
And don't worry about deflating my effort! All I need is one signature a day and by the time I'm 46, I can send the petition to Warner Bros.! But seriously, we can't look at this kind of thing as a lost cause. I think it's important to drum up support however I can.