Large scale zombie mmo style games started with so much promise, but have failed to live up to it. I've play more of the DayZ mod than the Day SA recently as the SA is too broken and not fun.

Anyway, competition is always good and a new contender using SOEs Planetside2 engine is H1Z1

This video is from January:

H1Z1, SOE's Zombie MMO

Live stream coming soon

and it'll be released on PC 'early access' style towards on Steam the end of May. It'll be coming to PS4 once it's finished and if its any good.