I've had more time to think about this now -- it would appear that directional prediction can be arbitraged away in a world where the future cannot be known. In general, however, through research, one can begin to divine a glimmer (or more) of the future direction of the underlying.

In that situation, someone with a reasonable guess at the future could absolutely murder uninformed arbitrageurs, right? It is my expectation that "correct" pricing of the options should fold in information about both the expected volatility and the direction of the underlying.