Change the voice: The task would have been completed by that time tomorrow.

Someone will complete the task by that time tomorrow.

Someone will be completing the task by that time tomorrow.

Someone would have completed the task by that time tomorrow.

None of these

Someone would have completed the task by that time tomorrow.

Passive voice "would have been completed" becomes "would have completed" in active voice.

The doer is assumed (e.g., "someone"), and the time expression remains unchanged.