A cutout for the chip has been visible on previous leaked photos; however, the new photos are high resolution enough to reveal chip markings.
The cutout doesn't appear to be required for the function of the chip, and it simply seems to be a space-saving issue. With the chip making that area of the display thicker than the rest of the part, the cutout allows the shielding to cover the remainder of the display panel evenly without adding too much thickness. As noted previously, the metal shielding is now glued in place rather than screwed in as on the iPhone 6.
Additionally, the new display panel is slightly thicker and slightly heavier. The iPhone 6s display (without front facing camera) weighs 51.2 grams versus the iPhone 6 part (with front facing camera) that weighs 49.4 grams.
Apple is expected to unveil the iPhone 6s at a media event on September 9th at the Bill Graham Civic Auditorium. Please follow iClarified on Twitter, Facebook, Google+, or RSS for updates.