It's been about a year since we had word of chapter 30 of Highschool of the Dead so it's anybody's guess when, if ever, the series will return. You can rest assured if there's any news I'll let you know so please stop bothering me about it.
On the plus side, if you enjoy Shouji Sato's torpedo tits, his series Triage X is still running regularly and you can grab the monthly raws for that at Scans of the Dead if you didn't know already. The scanlation has decided to once again wait for the volumes, but given the high amount of censored fanservice in the serialized version of the series that's probably not such a bad thing.
Good news: Fujimi Shobo announced an artbook which will contain artwork from HOTD, Triage X, and Fire Fire Fire for release on August 9th of this year (entitled 佐藤ショウジアートワークス, or "Sato Shouji Artworks"). The details of the release aren't yet 100% clear, but assuming I can get a couple copies I will see if I can scan it a while after it's released. Don't let that stop you from buying it if it's widely available, however. Although I certainly believe in the digital revolution and yada yada whatever, it's still of paramount importance to support authors and publishers.
For the HOTD volume releases, I've decided to hold off on releasing anything until I get everything together. I don't want to compete with the official US release and I want to be able to include as much as possible. It's looking like it'll be big enough that I'll probably have to release it as a torrent.