Blog 6 - Questions for the (un?)dead

I have just binged and caught up with Game of Thrones (minor spoiler alert in here) and the issues caused by the (un)dead in this story, combined with other pop culture stories focusing on armies of the dead gave me a question.

If the zombies, walking dead, (un?)dead, etc. need human flesh to survive, what is their plan for the long run? Have they considered what they will do when they have killed and consumed all of the living, leaving them - the dead - with no viable food source? Will the dead become vegans?

If this issue has been addressed elsewhere, I apologize. I am not intimately familiar with plans of the various zombie apocalypses.