Trust me, this is the real deal. Mark Gurman from 9to5Mac never posts anything that is not pure facts. He is the best source for Apple leaks at the moment.
For fall 2015, Apple is preparing an “S” iPhone upgrade that superficially preserves the exterior designs of the iPhone 6 and iPhone 6 Plus, but includes a collection of major internal changes. Now, a proven source familiar with Apple’s supply chain has provided us with the most extensive look yet at Apple’s next iPhone, sharing the first photos of the iPhone 6S’s external metal casing.
So the iPhone 6s won't have a dual lens camera as I and many others has reported. So Apple will probably not use the new dual lens technology from LinX - the Israeli company they recently acquired, until next year on the iPhone 7. But that doesn't say that the camera still protrude though. Maybe Apple will use the LinX technology somehow to get rid of the protruding camera. Or maybe the rumored 12 megapixel camera doesn't have to protrude? We will see.
And the Antenna lines are still there, so no new technology to hide them is there. So that rumor is also probably for the iPhone 7.
And the dimensions and thickness is identical with the iPhone 6. But the internals seems to reveal that the iPhone 6s will have Force Touch though. The internal structure reveals a lot of changes to the internal components.
So the iPhone 6s will definitely be an “S” upgrade with the same design but with better and improved specs and hardware as usual.