No, there is not in Forms 9. You could assign multiple users to the task in question so both would receive the task and could act on it. The other option would be to attach a timer event to the user task so after it has sat for so long, it can be re-routed to another user.

In Forms 10 they are introducing a new feature called Teams. My understanding is that a team lead or admin would be able to re-assign a user task from one user to another if needed. We will of course need to wait and see what is actually included when it is released this winter.