With the Civil War sesquicentennial rapidly approaching, I've seen no great indication from book publishers that it will be anything but business as usual. Do publishers hoard good titles in anticipation of extra-special Civil War anniversaries? I don't know, but, if they do, they are keeping quiet about it. University press blogs rarely mention their Civil War books, let alone promote them, and I haven't come across any notable marketing pushes, press releases, etc. from other publishers big and small that hint of any coordinated plans. The History Press is devoting an entire series to the sesquicentennial, and has been adding titles steadily for some time now, but perhaps it is telling that their own website does not even include it on their series list! [ed. 8/11 - a series page is up now]
Perhaps it is still too early yet for such announcements (and I suspect that might be so with today's short attention spans), but, if building anticipation is an important goal in publishing, no one has really started yet.