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It's a fair question but we should have no reason to doubt Wreck's info, which is what these comments are based on. He works closely with Play and I don't think he has passed on any duff info yet. They have also collaborated on exclusive artwork so Play would have no reason to provide him with false numbers and sour that relationship.
If 4k is the number he has been given then 4k it is. There have been many serious and longstanding collectors also suggesting this will go OOP very quickly and I would back them up and say get yours ordered if you haven't already.
And I'm going to take an educated stab at it going OOP much faster than many other steelbooks, closely followed by IM2, and lots of people being unhappy that they didn't listen to the warnings!