If something is described as being "in the pipeline," it means that it has not yet arrived but is expected to arrive in the future. This English idiom generally refers to plans that have not yet come to fruition but, if all goes well, will be fulfilled. In this context, "in the pipeline" is an idiom usually reserved for the plans and projects undertaken by businesses or other large institutions. The phrase gets its meaning from the fact that oil in pipelines is on its way from oil wells to refineries.
An idiom is an English phrase that may originate from a certain source only to have its meaning change as people use the phrase over time. The meaning of an idiom may end up being far different from what the meaning originally have been. Its meaning can even be entirely different than the definitions of the words it contains. Nonetheless, these phrases are useful in that they are extremely expressive and colorful. One such idiomatic expression is the phrase "in the pipeline."
When something is described in this manner, it means that it is going to arrive at some point, but it hasn't yet. In that respect, someone who uses this term to describe something is often making a promise about its eventual delivery. The person may also be reassuring his or her audience that this delivery will indeed occur, especially if it may have been delayed for some reason. As an example, someone might say, "I know I haven't delivered that report yet, but I promise that it's in the pipeline."
Companies often use this term for projects that have been undertaken or may even be simply in the discussion phase. Politicians also use this phrase to inform their constituents of some piece of legislature that is coming at some point down the line. No matter who is using the phrase, the implication is always that the thing to which they are referring may not be here yet, but it will at some point. Someone, for example, might say, "Our new model of automobile is in the pipeline and it promises to be our most popular to date."