Gary,
I don't think the "period" itself has been done to death, but certain "topics" have. Take, for instance, the SS. I mean, when Verlinden releases a 1/35 figure of a Waffen SS soldier taking a crap, you know it's been done to death! I'm afraid that one of my favorite subjects - US airborne forces - are falling towards this category as well. How many different ways can one depict a US paratrooper in Normandy? What about Market-Garden? Op. Varsity? Or airborne actions in the PTO?
World War II is definitely a historical period rich in miniature subjects; in fact, far richer than many think. IMHO, this is a historical period that definitely deserves far more exploration, especially while we still have the best resources around - the veterans themselves. I mean, how cool is it to actually email or call up the veteran that's the focus of your subject, just to ask about "uniform & field gear details"?