Jason,
Can you please try the suggestion given in following question:
How can you move a document with its version history to a new library?How can you move a document with its version history to a new library?
It says
Just moved (drag & drop) a file in Explorer View from one document library to another, and it did retain previous versions!
Obviously both libraries need to have versioning enabled.
Try it yourself.
EDIT: note that it ONLY retains the versions if you MOVE the files. It does not do so when you perform a COPY!
