here is my timeline, for the record (central time):
9/12 @ 12:03am - successfully preordered 128GB 6+ via AT&T's website
9/12 @ 12:03am - received "Confirmation for AT&T Order" email that said it "will ship in 14-21 business days" [10/2-10/13]
9/12 @ 2:33am - received another mail stating "Your order is in the process of being fulfilled" and shipping dates remained the same [10/2-10/13]
9/18 @ 4:22am - received "recent ATT order status update" email that stated "We are still expecting to ship your order on the dates listed" [10/2-10/13]
9/21 @ 4:00am - thanks to ideas & advice from the folks here, i checked local (MN) Apple store stock (which was sold out yesterday) to see if there was some in stock for today. i was pleasantly surprised to see a 128GB 6+ at 3 different stores and decided to call AT&T in the morning to find out if I could cancel my preorder and get it from Apple instead.
9/21 @ 7:00am - i called AT&T cust serv. 5 minutes after they opened (at 7:05am) and asked them if i could to cancel my preorder so i could go grab a 6+ via in-store pickup from an Apple Store today, and she said "sure, no problem! if the phone is available there, why not go get it?" she sounded as happy as i was... i said "yep", and that was basically that. she even stayed on the line with me until we verified my eligibility to upgrade was "restored" on the MyAT&T website account. i had my phone in the apple shopping cart before the call was over and paid for it a minute later.
9/21 @ 7:17am - received one email from Apple stating "Your order is being processed", "Well email you as your items become available for pickup", and "Available today. We'll notify you when these items are ready".
i'm hoping this will indeed actually happen today, as the system indicated it was available for pickup today, but either way, i'm now certain i'll be getting it sooner than October... thanks to this forum post.
thank you & good luck to everyone else.
* i'm not premier