Literally never, it's a completely dead franchise.
Author didn't want to continue a post apocalypse story after that earthquake and tsunami hit Japan and killed a few thousand people.
And he has a history of never finishing anything he starts.
>every fucker and his dog is masturbating over zombies at the moment
LOL guys fuck our zambie manga lets write another shitty one that isnt in vogue at the moment
japs hate money