To say "the jury is [still] out" on something means that the final judgment has not yet been made. The information has been heard, something is under consideration, and we are waiting for a decision to be made. The analogy is to a court case after the two sides have made their arguments but before the jury has returned a verdict (final decision). It may also express that we are waiting to see what the results of something will be. Example: "Its hard to say if what we did was the right thing. The jury is still out on it."