There is one thing that's a forgone conclusion at this point; We are very much in the decade of the Zombie. Just when you thought Zombies couldn't make it to the old west Rockstar goes and changes all of that. In the next DLC pack for Read Dead Redemption -- Undead Nightmare, comes a largely single player focused bit of content where a zombie plague has hit the frontier and John Marston goes about finding a cure to the plague. Also the DLC will include "brand new gameplay mechanics, weapons, zombie animals, mythical creatures and even a brand new secret location."
[Via Rockstar Games]