After discussing the publishing schedule with Choice of Games, it looks like Part 5 will be released in September, 2013. There is a ton of content I have to add to finish the many story-lines and provide suitable endings. Plus, I have a considerable number of features to add that have been requested by readers.
I work on Zombie Exodus at least 2-3 hours a day, while still working a full-time job. So hang in there, and hopefully the beta chapters hold you over!