The new iPad, the fifth, is expected to take after the iPad mini with a slimmer design, improved camera, and, while the screen will be the same size, the device will be narrower thanks to a thinner bezel. The iPad's processor, A7X, will get the same big boost as the iPhone 5s to 64 bit.
It's also likely the new iPad will feature the Touch ID fingerprint sensor, the same as the one incorporated into the iPhone 5s' home button. iPad mini will get upgraded to a retina display.
The event will also showcase new editions of the Macbook Pro and Mac Mini, and release dates for the new Mac Pro and OS X Mavericks.