The drama will include music by Akira Yamaoka, and will be released to coincide with the 300th episode of Hideradio -- this one is #296, and they are released biweekly, on Fridays. So ... two months or so? Of course, we'll then have to wait for some kind of translation, official or otherwise.
We take back what we said earlier. The real real surprise with this announcement is that Kojima actually announced something that isn't Metal Gear.