Here is the news from The Talking Dead main website. It doesn't mention who the mystery guest is. But it does mention that there going to be a mystery cast member guest. http://blogs.amctv.com/the-walking-dead/talkingdeadcom/I'd still lay money on Carol not being long for the world, I don't think her gimmick is going to work well for her in the long-run and it's going to get her in trouble, second to her would be Sasha who's been on the highway to the danger zone ever since Bob died, Tyreese's death only floored the gas. Third would be Tara who really hasn't offered much. Which would mostly make her death a meaningless red-shirt one.
I don't know, it seems like they have something in store for Carol now, although her death would add to Daryl's torment. I could see her lasting for a while yet.
Sasha is basically comic book Andrea now. They could kill her, but I have the feeling they want someone in her role at least for a while. However, if she has a lot of development in the next episode, as indicated by the previews, perhaps that could mean her end.
Honestly, if I had to guess that someone were to die, I wonder if it would be Noah. I know, that would seem like a waste, but I wouldn't really put it past the writers to do that. The reason why I think he might go would be because he's a guy with a messed up leg made to be a runner! I don't know exactly what the deal is with Deanna, but seriously, why make such a move? Does she want Noah dead? I wouldn't be surprised if they went out on a run and Aidan ends up getting Noah killed somehow.
They announced on Facebook that the special guest on the next Talking Dead is...
Kevin Smith
He was already announced. The mystery guest was not.
We don't know who that mystery guest is. It could be a past cast member, a present cast member or a future cast member. But it will be someone that will be involve in episode 13(Forget).