Since it's been 6-7 months between each release so far, I'd guess next April, but has anyone heard anything more definite?

I tried looking that up last night, but came up with nothing. I'm guessing in the beginning of next year.

That's what I thought too. I figured they'd start speeding up the releases by now, especially since they're selling well and they need to keep up with other shows' releases, but I guess not.