The problem is that the ipad 3 is now a dead end product. It's not even being sold anymore.
For example... when I got an iphone 4, the 3GS was still sold as the next price level model, when I got the 4S, same thing happened to the 4, and with my iphone 5, same went for the 4S... when I got the ipad 3, the ipad 2 then became the value model... which when the ipad 2 hit the market, the original ipad was sold along side at a cheaper price...
now comes the ipad 4... ipad 3 becomes the value mod... no wait... that's still the ipad 2...
basically the ipad 3 will lose more value...
I don't buy apple products as investments, but I do rely on the desirability of them (ie. resale potential) so I can upgrade to the next new product and sell the old one... buyers in the used market may view the ipad 3 as if it had something wrong, since it's not longer carried at all by apple, just after 7 months on the market...