Become a MacRumors Supporter for $50/year with no ads, ability to filter front page stories, and private forums.
If it is shipped from China update will be on Wednesday and if it is from home country then on Thursday, this is my guess. I believe Apple has already started shipping to individual country's warehouses and will ship to individuals on Wednesday from China.
 
When I ordered my iMac last year, it was in stock and ready to ship. Even then I was given a four day window and not a firm shipping date.

Very few companies give out exact shipping/arrival dates. There are too many variables outside their control.

This has NEVER been the case with any launch day shipments for iPhones. If you preordered early enough to get a launch day phone, the "delivered by" date (even when the order was still "processing") has always only been one date....The launch date. Never a shipping window from x to y.
 
Register on MacRumors! This sidebar will go away, and you'll see fewer ads.