I like the idea that the Governor may be behind the sudden increase in walkers going to the prison and in the surrounding areas. It wouldn't surprise me that next week when they show Rick come back without Carol he tells everyone that the walkers got her and the guy that Rick gave his watch to is at the prison. That way Rick doesn't have to try to explain why he left her and doesn't have to deal with a pissed off Daryl that wants to go look for her, and everyone gets to see that the guy made it to the prison only to have him killed later on. The only ones I can see him telling is Hershel, only to see if what he did was the right thing, and Tyreese so he knows that Rick did something about the "murder" of Karen.
I think the Governor will be back near/at the end of this season. It might lead up to the start of next season or finish of this one, but I expect him to come back. I'm thinking he got with a group that is just as messed up if not more messed up than he is and they are now fallowing him. I'm thinking that Carol may somehow come back at this point in time and be the one to kill the Governor. At that point everyone will be wondering what is going on and Daryl and Tyreese will be ready to kill Rick. Both for different reasons. Daryl because he just found out that Rick left Carol on her own, and Tyreese because Rick didn't kill her like he let Tyreese thinks he did.
After that I think Daryl will want her back and she will choose not to stay and walk off. After she walks away I see it going one of two ways. The first being divisions in the groups Daryl along with others going with Carol, some leaving with Tyreese and others staying with Rick. It would't surprise me if Carl leaves with Carol. The other thing I can see happening is Daryl wanting to go with Carol and he stopping him and that she wants nothing more to do with the group. I still think Tyreese will leave on his on and that him or Carol will replace the Governor. Hell maybe even both.
I do expect the talking from Tyreese to stop not long after it starts once he sees Carol. Hell I could be wrong about all that I just typed and he could kill her on the spot and it be him that becomes the next Governor.
This is all being said without having read the comics. So I have no clue what happens to Carol or Tyreese at this point in the comics. I know the show is trying to do some things different than the comics so what ever happened to them in the comics may not happen in the show.
This is all a guess and sadly may be better than what really does happen in the show.
On a side note a friend of mine just showed me this the other day: