Willing to bet the traitor is Black Spider. I think the color is a hint. And he was one of the guys who was with the team at the beginning who wasn't with the Squad when they first went after Basilisk. It's not El Diablo because we saw how we got on the team. And I doubt it's the Savant character since he cut a deal with Waller.
So I was a little unsure as what to what was going on with the roster shake-up (of sorts). Savant was released from the prison and is back to vigilante work, right? If he was released from the prison after only one mission what did he even do to end up in prison in the first place? Jaywalk?
And yeah, I get the sense that Black Spider is the traitor since he has no real reason to stay anyway.