Or he plays the I was once a con and now a bot card but still a con and working for lockdown the whole time. Wouldn't that be a shocker!
It's just a placeholder for the actual thing. Drift will be released under the name "Autobot Drift", why would they label him as mystery villain? Only decepticons that will be released are Lockdown and Stinger so it's one of them.
But the thing is, Drift's silhouette is not a place holder, there is going to be a Drift POP figure. So is he a traitor?
Or he might get killed/destroyed, and is resurrected by Harold Attinger as Bludgeon . . . skull for face, and all . . .
I was thinking the opposite, like his back story, but instead of being Deadlock, he is Bludgeon changing sides. That or maybe Bludgeon will not be in the film at all, but have toys that are just a recolored Drift.