They are saying now that Frank didn't fire his number 2. Frank decided to stay on as showrunner for the second season, and so his no. 2 decided to go on to something new. He apparently is a big demand writer, and didn't want too many big guns running the show. Makes sense.
As for the others, we'll have to wait and see. But honestly, I trust Frank. And so does the cast, and Kirkman. I'm not worried at all. In fact, i'm thrilled that Frank is staying with the show. It just proves how much he loves the material, and wants to be involved in all of it!