iPhone 5S:: Our best guess on the release date, specs, and availability for Apple's next iPhone

In a world where almost nothing is certain, this is basically certain: Apple will be having an event on September 10 where the company will announce two new iPhone models. Or so we think.
Despite CEO Tim Cook's pledge to double down on secrecy, it seems like we already know everything about what will be shown: from extremely detailed purported photos and teardowns of the external casing to color options, the iPhone 5S and the iPhone 5C seem inevitable. The rumors have been fast and furious, and increasingly seem to confirm a similar picture.
If rumors are true, Apple is set to bifurcate the new iPhone lineup into two lines: a more budget-targeted, plastic-backed, candy-colored "5C," and the higher-end iPhone 5S, which looks exactly the same to a casual eye as last year's iPhone 5.

What we think we know

Design: Think iPhone 5, with additional colors
Last year's iPhone 5 wasn't revolutionary, but it did amount to a top-to-bottom restyling and re-engineering of the iPhone 4/4S look into a totally new product. The 5S, on the other hand, looks like last year revisited, down to the two-tone metal/glass back and chamfered edges.
That might make this iPhone feel like one of the most boring iPhone releases ever, but it's a common pattern: new iPhone design one year, bumped-up version in same design the next (iPhone 3GS, iPhone 4S).