Zombies are so overly used right now, I can see why people are absolutely sick of it. That being said, I love zombies in games. A zombie game will always grab my attention.
That being said, I don't feel like a zombie mode would fit well here. I feel like R*'s resources would be better used elsewhere. Would I like to see a zombie survival game put out by R* using their current tech and know how, with a heavy emphasis on survival and not zombie slaughtering??? Hell yes. I don't want a watered down version within gta v though, especially if it detracts from gta itself.
Yes, I've seen trailers and info on the upcoming game: State of Decay. Looks pretty alright, but I would basically like to see that same concept copied and put in the hands of R* and the RAGE engine. Plus, have multiplayer included. Not a mode, more MMO style drop in and drop out as particular individuals