In terms of the investigation and the direction of the investigation, I definitely think this is a cold case. But there is one exception and that is the audio/video Liberty German captured with her phone. If someone can sit back and distinguish that from the two bad sketches, then I think this case could change tomorrow.
The case of Abigail Williams and Liberty German is a cautionary tale. It is an example of the fact that even with evidence, a voice, and a picture, you still need someone to connect it to. Detectives still need to do their jobs as thoroughly as they would if they did not have all that evidence. And they need to be careful to remember to consider every case on a case-by-case basis. Public places present problems because they can be accessed by anyone. This would be especially evident if the killer is not from Delphi, IN or the surrounding area. The idea that he worked, lived, or traveled to Delphi covers just about any sort of association since in order to know a place, all of us usually become familiar with a place for some reason that requires us to have travelled there.
This is definitely a cold case now. I do not think the detectives are going to solve this case by something they do. This is what I mean by "cold case." If this case is ever solved, in my opinion, it will be because of a 14 year old girl pulling out her phone and hitting record.