Something in the pipeline is in progress and on the way. For example, a new game in the pipeline is being worked on by the game developers and will likely be released soon.
The phrase in the pipeline is most often used by businesses that create products like TV shows, video games, or other consumer products. If a company has a new product in the pipeline, it means that it's being worked on but hasn't been released to the public yet. This phrase suggests that work is actively happening behind the scenes, moving things toward completion.