well, it's been announced for the firestone beer fest in early june. unless they brewed a super tiny batch or that's an old keg (unlikely, i feel) or something, i'd guess late may/early june?
It has been released since August approximately every 3 months, last release was 6 weeks ago so, 6 weeks seems about right, Kyle and/or Eric just might chime in with an answer. Althought their 6th anny might be occupying their labors at this juncture.
They make small batches for beer events. They had fresh kegs up for SF Beer Week, but didn't do a bottle release then. Although I guess they did a release about a month later, I forget exactly when the last release was.
I would guess the next public release would be in August. They may be making the next batch now for the events upcoming events.