It is not clear yet if the additional allocation of units will have much if any actual impact. It could be nothing more than a better verification from the manufacturers to the retailers on exactly how many units they are getting and after balancing the numbers, the retailers figured out that they had at least some additional units that they could sell.
Launch day availability seems to be all but gone in North America for the PlayStation 4, while Day One Editions of the Xbox One seem to be sold out now across the board, but it seems that most retailers are still accepting orders for the Xbox One without a confirmed delivery date.