What's the difference? In short, Timbal and the other mods oversee the forums, while the CMs (like Drysc and Nethaera) oversee the community. As you can see from that last link, Blizzard still has the CM help wanted ad up, and so it seems to be a pretty good guess that Tseric hasn't been replaced yet.
Or maybe he won't be. According to what I've heard from players, the forums need more moderation than management-- while Blizzard's CMs have been focused on the forums, I'd suggest WoW's community isn't really there anymore (if it ever was, really). It's either in game, or on sites like WoW Insider. Lots of players have asked for a change in the forums, either a crackdown on the shenanigans that seem to take place there, or just a way to make them more relevant to the game. Hiring Timbal as a moderator might be a step towards moderation, and a step away from relying on CM activity in the forums as Blizzard's way of managing their connection with the WoW community.