My take is that this "newer generation" of tools seems to focus on combining configuration management with orchestration. Chef and Puppet let you define the static state of the world but leave it up to you to figure out how to transition when something needs to change.
On the other hand, Ansible works well as simply a remote task runner (like Fabric). Salt is the one I have least experience with, but I had a conversation with the creator once and he seemed excited about the orchestration possibilities with Salt. If I understand correctly you can react to events that get triggered either manually or based on a condition on some other server you're managing. So both of these tools make it easy/natural to do something like run a rolling restart of a group of servers.
I'm not finding the new generation term particularly meaningful.
One thing that was somewhat unique about Ansible was it was designed for rolling updates as the initial use case, and the desire to solve deployment problems rather than just CM problems.
Everybody tends to view orchestration differently, so see our take:
On the other hand, Ansible works well as simply a remote task runner (like Fabric). Salt is the one I have least experience with, but I had a conversation with the creator once and he seemed excited about the orchestration possibilities with Salt. If I understand correctly you can react to events that get triggered either manually or based on a condition on some other server you're managing. So both of these tools make it easy/natural to do something like run a rolling restart of a group of servers.