It is a 6.65" AMOLED display!
The display resolution is 2340 x 1080 pixels.
I interpret it as, although the screen is bigger than originally proposed, the overall size of the Astro should not change...
I agree. The 2160 x 1080 resolution of the Cosmo and Gemini screens, gives them an aspect ratio of 2:1 (but I'm going to use the more common 18:9) "units". Phytagoras gives a diagonal of SQR(18^2 + 9^2) or about 20.12 "units". Knowing those "units" equals 5.99", we can divide the inches by the number of diagonal "units" and multiply with 18 to get the width, or by 9 to get the heigth, which then, if desired, can be multiplied by 25.4 to mm, which would give an active area of:
5.99" / SQR(18^2 + 9^2) * 18 * 25.4 = 136mm
5.99" / SQR(18^2 + 9^2) * 9 * 25.4 = 68.0mm
Measuring my Cosmo with a ruler, that seems about right. The outer dimensions of the actual display module is, of course, a tad bigger.
The 2340 x 1080 resolution of the Astro, gives it an aspect ratio of 2.1666…:1 = 19.5:9, and it has a diagonal of 6.65", so if we plug in those numbers instead, we get an active area of:
6.65" / SQR(19.5^2 + 9^2) * 19.5 * 25.4 = 153mm
6.65" / SQR(19.5^2 + 9^2) * 9 * 25.4 = 70.8mm
Again, the actual display module is, of course, a tad bigger.
While the particular OLED screen chosen by Planet probably is flat, given that OLED screens exists, that can partially wrap around the long edges of the device, we know it is possible to make OLED screens where the width of the display module, is virtually the same as that of the active area, so, to me, it seems the Astro display chosen by Planet, probably would fit within the 171.4 x 79.3mm footprint of the current devices, and maybe even with in the 164 x 76.6mm preliminary footprint (from the crowdfunding) of the Astro, though, as the Gemini and Cosmo keyboards are 164mm wide, I'd guess that preliminary width was ever only a placeholder. The current keyboards are 70mm tall, so that might fit within the preliminary 76.6mm, given that the Astro probably won't need any magnets (so, maybe, finally, there will be a working compass) and will have its hinge stuffed under, rather than to one side of, the keyboard.