Klostermann have news of a volume of Heidegger’s Gesamtausgabe in preparation for 2011 publication here. Volume 86, entitled Seminare: Hegel – Schelling, it’s projected to be 936 pages, which might well be the longest yet – GA16 was just over 800 pages, and that’s the only comparable one I can think of. It includes material from six seminars between 1927 and 1957, including the 1934-35 introductory seminar on Hegel and the philosophy of right which Heidegger used as a means of discussing political philosophy. Should be interesting, although some of these seminar notes in previous volumes are pretty cryptic.