Looks like Treyarch won't be following in big brother Infinity Ward's "Modern" footsteps after all: A job listing for a CoD level designer mentions - among other things - an interest in historical research.
Last October, Noah Heller - Treyarch's senior producer for Call of Duty: World at War - told OXM UK that WaW was likely to be the last game set in World War II that the company would develop (at least for a while), leading many to wonder if it would be joining series co-developer Infinity Ward in the Modern Warfare arena.
However, a job listing posted on the Treyarch site (and spotted by OPM UK) indicates that the developer's next game will still be set sometime in the past: Treyarch is looking for a level builder & designer who possesses not just the technical acumen and experience to craft a well-made mission, but a willingness to "[r]esearch subject matter for history and look of the level."
Obviously, the wording is vague, since "history" could arguably mean something as relatively recent as, say, the first Gulf War. However, rumors back in May suggested that series publisher Activision was looking to license a very specific type of music: "Vietnam War era tunes, as well as Cuban, African, and Soviet Union music." Said rumor led many gamers and journalists (including yours truly) to speculate that Treyarch's next CoD would be set during the Vietnam War - or, perhaps, the Cold War as a whole.
While - if true - this wouldn't be the first war game set in 'Nam, it would be an interesting direction for Treyarch to go in. In comparison to WW2, which is generally perceived in pop culture as a "good war" in which the heroes triumphed over an undeniably evil foe, Vietnam occupies a decidedly different area in terms of cultural memory - especially here in the States.
Still, I'd like to see it happen. Treyarch is a competent developer in its own right, but has largely been in the shadow of Infinity Ward for the most part. Branching out in a new direction - not just for the company but for the series as a whole - would be a chance for the Treyarch team to strut its stuff without (quite so many of) the endless comparisons to the IW games. Besides, it's a (relatively) unexplored era of warfare as far as games are concerned, and if done right could be a damn interesting game.