At Duke, at least, six of their nine journals - yes, nine journals - are moving to a digital-only format. Only the Alaska Law Journal, Law and Contemporary Problems, and the Duke Law Journal will continue to appear in paper.
I haven't done any research on this issue, but I imagine that increasing numbers of secondary journals are moving online. This decision could trigger reconsideration of this issue by a flock of other law schools. In tight budget times, paper journals may seem like a pretty ripe target.