Future iPad-mini's Resolution = iPad Resolution. Pixel Density = iPhone Pixel Density
According to this news/rumor ...
Display area of the iPad-mini = 29.6 square inches.
Current Resolution = 1024 x 768 = 786432 total number of pixels
Pixel Density = (Total Number of Pixels/Display Area)^0.5
Pixel Density = (1024*768/29.6)^0.5 = 162.99 ≈ 163 pixels per inch.
Doubling the Resolution (converting to Retina):
iPad-mini with Retina Display area = 29.6 square inches.
Resolution = 2048 x 1536 = 3145728 pixels
Pixel Density = (2048 x 1536/29.6)^0.5 = 325.99 ≈ 326 pixels per inch.
Same pixel density as iPhone. Seems likely to be released.
Same resolution as current iPad. Cannibalizing its own newer iPad? Not happening bro ...
... But they have done this with the Macbook Pro vs Macbook Pro with Retina Display. Over there exists a significant price gap too ... Not here though. $329 for iPad-mini will be less than $499 and you get a lighter, thinner, more portable than current iPad product with same battery, power and resolution? Unlikely. People would then only buy iPad-mini. The non-mini iPad would have to be extremely good to demand that much of a market share.
Seems very difficult to say though.
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Vector graphics would be useful for graphical elements. An alternative that would do a good job most of the time is to use high resolution bitmap graphics, and let the OS downscale the image.
Don't think that can happen, though it seems like a good idea. At the same time, I can't imagine why wouldn't someone come up with vector images ...