The retina screen for the next iPad mini 2 maybe will be released at the same time. Meanwhile, Apple already doesn't let owners of the first iPad download new versions of iOS - let it rot and chuck it into bin.
iPad 5 to be thinner - and land in March: report
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It's like me complaining that I can't install ICS, let alone JB, on my old Galaxy S.
Even if I could, I wouldn't want to. It would crawl so badly I'd probably smash the phone against the wall out of frustration.