Does POP paradigm allow for inter-state data-passing or more synchronous return data?

Yes, both of these aspects of Terraform and Ansible will be possible through a POP enabled Salt, but this will not happen immediately. As for synchronous return data, POP allows all of the components of a larger application like Salt to be broken up into pluggable components, so we will be able to make a pluggable transport layer. As time goes on I am planning on making more and more layers to POP until we have a strong remote ex system that looks somewhat like Salt, but should be faster and more feature-rich so as to enable these sorts of features. As for inter state communication, the Idem project already has the beginning of this, and as you said, these systems are difficult to make smooth. I am iterating on some ideas there to try to make inter state communication as smooth and easy as possible without rushing out a solution.