JSONB is definitely in 9.4. We used that at the company I worked at previously. There might be improvements to it in 9.5 that I can't recall but it's definitely usable and production ready in 9.4

EDIT: Looks like [1] talks about what he was mentioning, there's a number of functions they added to improve the use and experience in 9.5.

[1] https://www.compose.io/articles/could-postgresql-9-5-be-your...