or it could be Silver. Major plot twist???
And if that were the case, it'll be rewarded with a nice hefty dose of dull surprise.
I can see it, whatever Silver does in the past will be the cause of his future happening, not exactly the most original idea ever when it comes to a time travelling storyline. Time travel stories can be a bitch to write especially when the goal is to change the future.
As for the traitor, having Sally as it seems the most obvious choice giving her current state, and as such can hardly be considered shocking and surprising at all. But we don't actually get to see the poster after Harvey has marked off Antoine and the other two and while Sally does occupy the top right corner and the way the markers are placed on the poster when we see the back of it seems indicate it's her and if it is her, they might as well of shown us now instead of cocking about because it wouldn't take a genius to figure it out there. But I noticed the way Harvey holds the poster seems to change, like he is turning it, so perhaps the idea is to trick people into thinking it's Sally and it'll be someone else. I dunno, just a hunch.
It'd be more of a shock if say Rotor was the traitor or hell, even Sonic. Having Sally as the traitor seems so bloody obvious at this point with her being roboticized and loyal to Eggman that if Flynn pulls out "Surprise! It was Sally as the traitor!" then the dude seriously needs to learn how to pull off a shocking revelation, because the best ones are the ones that leave no clues at all and then BAM! they show up and smack you in the face! A good example for this would be the
Doctor Who story 'Earthshock' where the first episodes cliffhanger revealed the enemy to be the Cybermen who hadn't been on the series for 8 years and there were no clues at all about who the monsters for this story were.
But anyways, it's still to be revealed. I know people are bitching about this whole traitor thing and they are certain it's Sally, but again, if it were obvious, they might as well have shown us. All we can do, as readers, is wait for it to be revealed.