It's been over a year and a half since the release of the K-on! movie. There's no actively running manga. There are no announced plans for new manga or anime. The K-On! Hōkago Rhythm Time arcade is pretty much the latest major bit of fuel for the K-on! faithful. This hasn't stopped otaku from continuing to celebrate the July 2nd birthday of keyboardist Tsumugi "Mugi" Kotobuki.
In honor of her birthday, you can download a special Tsumugi Symphony fanbook PDF at http://mugi.nmou.in/