I was up at 3am, got through with my iPad app at around 3:40. Online store was still not open yet. It did take entering the info about a dozen times before my purchase of a 6 plus 64 GB space grey was completed. I got the confirmation email shortly thereafter. Delivery is scheduled for next Friday the 19th.
I followed up with the tracking link this afternoon and it shows order is being processed for delivery on the 19th. I also see authorization for the transaction on my credit card. With this info I am very confident that Apple will deliver as they have done so in the past.
I don't trust the carriers with delivery dates because they are just middlemen and can't promise anything without confirmation from Apple. This is where the confusion stems from.
So, yes it's pretty much a guarantee that I, and many others with delivery dates showing the 19th from Apple will receive their 6 Plus next Friday, or at the latest Monday.
Anyone who doubts this can come back to this thread next week for confirmation.