The iPad 2, 3 and 1st generation iPad Mini are all ineligible and excluded from upgrading to iOS 10.
They all share similar hardware architectures and a less powerful 1.0 Ghz CPU and 1 GB or less of RAM (the iPad 2 only has only 512 MBs of RAM) that Apple has deemed insufficiently powerful enough to even run the basic, barebones features of iOS 10.
Why would you want to upgrade, to iOS 10 on an old iPad model, like an iPad 4, anyways?
Since iOS 8, older iPad models such as the iPad 2, 3 and 4 have only been getting the most basic of iOS features.
Older iPad users get none of the newest and coolest cutting edge features that newer model iDevices, with better hardware specs, can handle with more aplomb.
Plus, the iPad and 3 are the only two supported models left that use the much outdated 30 pin dock connector.
The same iPad 2 users who whined and moaned and groaned that both iOS 8 and 9 slowed down the performance of their iPad 2 models would come back, once again, in angry droves, with even more complaints of slowdowns under iOS 10.
Plus, the initial release of iOS 10, at the moment, seems riddled with bugs and undocumented feature omissions that current iOS upgraders are, currently, struggling with.
Getting an iPad 4, at this late date (already 3 generation past this model), is not a very good decision.
You aren't going to get much more functionality with an iPad 4 as that iPad is only getting the barebones features of iOS 10 only becuase it has a CPU faster than 1.0 Ghz and has a lightning connector.
The iPad 4 still only has 1.0 GB of installed RAM.
The storage sizes have no bearing on performance.
You are much better off looking at Apple's refurbished store where you can get older, but still newer model Apple products, at a significant discount.
These products are treated as new and carry the same Apple AppleCare warranties as brand new Apple products!
You should look for better spec'd iPads like older iPad Air 1, iPad Mini 2 or 3 and even the more recent iPad Air 2 ds these are nearing two years old.
Newer model iPads will take more advantages of all the features in the latest iOS 10 that an over 4 year old iPad 4 won't.
I got my mom to purchase a 128 GBs model iPad Air for nearly $200 off its regular retail price from the Apple refurb store and we purchased two year AppleCare + for it, as well.
Here's some examples.
http://www.apple.com/shop/product/FF015LL/B/refurbished-ipad-air-wi-fi-cellular- for-att-128gb-space-gray
http://www.apple.com/shop/product/FF025LL/B/refurbished-ipad-air-wi-fi-cellular- for-sprint-32gb-silver
(You don't need to activate the cellular service to use an iPad with cellular. You can still just use the Wifi part)
http://www.apple.com/shop/product/FH182LL/A/refurbished-ipad-air-2-wi-fi-64gb-go ld
Apple refurbished store here.
http://www.apple.com/shop/browse/home/specialdeals
Also, if you live in the U.S or where ever the up and coming holidays are being celebrated, you can wait until Black Friday for, perhaps, even better deals than this.
Good Luck!
