Patch 1.6, which includes Map Pack 3 for PC, deploys next week. This time I am going to get his name right and attribute the news to Josh Olin, the Treyarch Community Manager.
Map Pack 3, of course, includes the multiplayer settings Battery, Breach and Revolution, plus the Nazi zombie map Der Riese. Unlike the consoles, however, PC players get this for free.
There are some other exploit fixes and issue correction. Additionally, Olin says Treyarch does "expect a concurrent release of the Mod Tools 1.4 package, Linux dedicated 1.6 bins, and the Steam 1.6 day-of-date with this patch." Full details at the link.
Patch 1.6 Details [Call of Duty Community Forums, via Blue's News]