What do you do, if an item on your "waiting for" list turns into "actionable"? Will you move it to "next actions"?
Most of the time, I would add an action to contact whoever I was waiting for. I would still be waiting, so I would leave it on my list.
The exception would be if I was giving up on waiting, in which case I would remove it from my list and think about how else the project could be achieved.