Great question. Hopefully someone can chime in on this question.
Does seem odd that they would delay orders only to ship you the model you ordered and not the refreshed. If the refresh is really different, you think they would have to stick with the model you ordered. But why delay it unless the stock levels are so low that they have difficulty ensuring orders are filled.
I remember reading on these forums (I think) that someone had actually ordered literally 1 day before an update and Apple had notified him to tell him that he was going to be receiving the updated model, which is lucky, and good for him.
If there are actually a lot of stories like this and had I known, I probably wouldn't have cancelled the order but I guess it's a too late now.
I thought, well if the MBP's are (possibly) being updated on Thursday and I'm going to possibly receive the older model on Friday, I may as well cancel and wait and then re-order. There was that glimmer of hope that the delay was only because they were planning to send me an updated copy but again, I've only read one story that someone had received the update instead of the one he had ordered.