What iPad 2 didn't get?

There are five specific things Apple could have added but didn't. We're going to break down what they are and what impact they'd have on the product:
Retina Display
Apple's "Retina Display" technology first appeared on the iPhone 4 and later made it into the latest version of the iPod Touch. Marketing speak aside, it's a high-density pixel display that packs in about four times the number of pixels as standard displays. How this trickles down to apps is text with smoother edges and the capability for developers to add more detail.

An SD card slot/USB port:
The iPad has largely been positioned by Apple as a companion device to traditional computers. But that doesn't mean people aren't using it for things they'd normally do on a computer, such as plugging in their camera to store, edit, and share photos they've taken on their digital camera. Apple's solution up until this point has been to sell a camera adapter accessory that uses the iPad's 30-pin plug to interface with either an SD memory card, or any USB camera.Thunderbolt connectivity
Thunderbolt is Intel's super fast port that debuted just last week (read our FAQ on it here). So far, it's only available on Apple's MacBook Pro line, which got a refresh the same day Thunderbolt was formally announced

Near Field Communications technology
Near Field Communications technology, or NFC, enables devices to exchange information with one another over short distances. Think of something like the Bump app, which uses an intermediary service to exchange information between two devices that are tapped together. Well, NFC goes the next step, and actually sends the data between the two with no middleman.4G
And to cap off the list of things that could have made it into the iPad 2 is 4G, the successor to the 3G cellular data networks that promises to bring significantly faster wireless data speeds.