I had planned to wait until I had more information to post about this, but I guess I might as well deliver the news since everyone else is.
It seems Highschool of the Dead is finally returning from its hiatus, which began in March 2011 after the release of Chapter 29. Both the cover of the Full Color Edition Volume 5 (below) and this month's Monthly Dragon Age announce a "restart" or "reboot" of the series. No date has been made apparent yet, so we will have to wait until the FCEs and magazines are released on the 9th to see if there is a date given.
Here is the FCE cover:
What makes me a bit nervous is the three large kanji on the band. HOTDcups tells me they translate to something like "reboot," and Google says they mean "restart." In either case, there seems to be a possibility that the series is not returning by continuing the main story, but rather with a new story or a retelling of the original. This would be a major disappointment considering where the story left off.
I personally think the series will make a full return to the original story, but we'll have to wait for more information to be certain. Hopefully I'll have something definite for you within the next few days. Stay close!