In terms of size, you’re correct, it’ll be roughly 11.25”. But....Oh yes, this is essentially what I wanted! I was thinking 11.5" but this would do. I'm hoping we can get the 12.9" UI scale in this device. Let's do some math:
12.9" resolution: 2732 x 2048
@3X retina: 4098 x 3072
What I'm hoping for:
~11.2" iPad Pro "4K" at 4098 x 3072: 458 PPI
iPhone X PPI: 458 PPI (Apple sometimes likes to keep PPIs across devices, especially if this thing ends up with an OLED, but in all likelihood I don't see that happening until the generation after this new one)
iPad Pro 10.5" physical dimensions: 9.8" x 6.8" = ~11.9" diagonal to work with and contain ~11.2" display
iPad Pro 10.5" display dimensions: 8.4 x 6.3 = 10.5" diagonal
iPad Pro "4K" 11.2" display dimensions: ~9 x ~6.7 = ~11.2" diagonal
Top and bottom bezel: 0.4" (enough to contain Face ID sensors, camera, etc)
Side bezels: 0.05" (basically none, though I've been rounding some, so it might be up to 0.1", it's all hypothetical anyway, or maybe they'll make it just slightly wider like the iPhone X and so that people have to rebuy accessories).
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Alternatively, they could "upgrade" the 10.5" to 2732 x 2048 and the ~326 PPI would be the same as the iPhone 8.
Another option is to scale up the 10.5" resolution by roughly the increase in size to 11" to maintain PPI and then take that @3X gives you nearly the same 401 PPI as the iPhone 8 Plus.
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Anyone else come up with something better?
You are forgetting that the aspect ratio will be changing to around 3:2 rather than 4:3. That will explain your incorrect bezel calculations, and also mean that the resolution would be different to achieve an iPhone X pixel density. Having a 458ppi (or even just 326ppi) would be brilliant but I think that’s something they will do with the move to OLED.