This is good news, indeed. While zombies really haven't been announced, there is obvious reason to believe that it will be in the game. Here's why I'm nearly sure it will be in the game:
Why would Treyarch hint at things like this, and state various times that they have listened to the fans' requests, if they weren't going to include such a mode?
It's one thing not to mention things like that, and not to include them. It's another thing, however, to mention these sort of things, and then not provide them, when they know very well that the community is hoping, and some event expecting a zombie mode.
If a zombie mode is indeed going to be included in Black Ops, I think there will be multiple variations and improvements from the zombie mode we all know and love from World at War. Where could such improvements be made? Zombie behavior? New concepts? Who knows!