Streaming exclusively to US users, Plex will roll out the content later this year. There's no programming line-up yet, so we don't know if users will be treated to current movies and TV, Warner's collection of classics, or some combination of the two. One detail that Plex did clarify upon is that the content will be free; you won't need to be a premium member of the service.
The Warner Bros. movies and TV shows will likely be just the beginning of Plex's ad-supported content, as the company plans on working with additional media partners to expand its catalog. So while the main draw of the app will still be the ability to stream a personal media library, it may eventually become a centralized app for on-demand content across networks.