Way too much. I don't see Game of Thrones getting to 12 Seasons and by comparison the scope and amount of characters and story telling pales in TWD.
This is bad news imo because it means they are planning ahead of Kirkman's writing. I don't see you getting 7 seasons out of what's left. I do like the idea of the show going as long as it can but let's let it get there on it's own.
The good news is they didn't get greenlit for more than 1 season at a time. Burn Notice got renewed for like 3 seasons in one go and it ruined the show because the writers knew they had a safe job and stopped trying.
At some point they are going to have to introduce either zombie animals or fast zombies or smart zombies. There is no way in hell they can make it to season 12 without doing something like that.
I KNOW Kirkman said he will never do that but Money Talks and if ratings start to go low they will definitely try to make the zombies more dangerous. (They already tried that with the "Sick zombies"
I wouldn't be surprised if by season 12 some of the zombies are starting to talk