Look at how Dawn of the Dead ended. The guy and girl leave the mall in a helicopter, and that's the final shot. We don't know where they're going or what happens to them. And I love that ending (that's why I hated the remake) Or in the original, everyone dies, but we don't see what happens to the world outside of this small sphere in which the story takes place. That's pretty vague So this one is in no way a departure from the previous movies.
Regarding the thinking zombies, you're completely missing the point of this movie. It is an evolution of the ideas presented in previous movies. Why do the zombies come to the mall in Dawn? Because they continue to act out in death what they were programmed to do in life. They're like computers, only capable of doing what they've been programmed to do - no true independent thought. But you can program a computer to appear to be thinking. I don't think the leader-zombie was so much thinking but rather acting out his programming to a greater extent than other zombies. Cholo's actions at the end of the movie were completely in line with this concept.
You could also think of Land like a sort of nature program. If you go to the jungle for the first time, you're going to see a bunch of monkeys jumping around in the trees and screaming and eating bananas. Doesn't look like much. But when you spend time examining and watching and learning about the monkeys, certain traits begin to appear. They're a somewhat organized society, with a hierarchy between the members, and each one has their own idiosyncracies. They use tools. They communicate. They groom each other. You get the idea. Land is a similar look at the zombie world. The other movies dealt with simply surviving the zombie attacks. Now that a safe haven has been created the zombies can be examined from a safe distance. That's how I see this movie. These traits may have always been there, but it's only now that the living can begin to see them.