When they updated the iMacs in August of 07 they were released the same day as the announcement. There is no reason why the Macbooks should be the same.
especially given all the talk about them already being shipped and just waiting to be sold (from warehouses)
yes those were rumors, but they only make sense. Why would apple make the wait longer when they know supplies are dwindling/gone and theyve had a huge amount of time since the last update to get everything finalized (i believe we had to wait for the air/iphone because they were still trying to get the sheer volume produced so they wouldnt run out....not that it worked in the case of the phone)