Sorry to disagree. My local Best Buy, Amazon, and B&H Photo (where I buy my camera equiptment and a good place to buy computers with no tax and Apple Care for a great price) are all fully stocked. This could be the stores knowing the product life cycle and trying to reduce inventories by ordering less and less with each restock.
I could easily see them releasing after the stock is truly depleted so no one needs to discount to move out old inventory which is probably more profitable at the moment. But, I don't know and can't see any reason at this point to hold off introducing a new computer in fear of compromising iPad sales.
Anyway, the complete lack of any tangible rumors for a 'this Tuesday' release is keeping my expectations low. I am placing the odds, based on nothing, at 1:4 for this Tuesday and 4:5 for the next four Tuesdays. If not this Tuesday I may instead buy a refurb imac. Apple told me that I could return it within 30 days (of placing the order) without a restock fee if I exchange for a higher priced item. It looks like a refurb imac 3.3 and a MB might cost about the same as a high end 15" MBP. Anyway, the wait goes on.