The new Nexus 7 will likely have many new features that the Nexus 7 is lacking. Like it might have a micro HDMI port. That was many people's biggest pet peeve with it was it lacked one, so you can't put these awesome graphics on the big screen. It could also a micro SD card slot, that would allow you to expand your space without collapsing you wallet to much.
Secondly, the new tablet will be faster. It could feature a Tegra 4 chip( check out my competition between them here) The Tegra 4 chip will be amazing. Other reports state it will be an s4 pro, which is nothing to scoff at and a big improvement over Tegra 3, but not as big a Tegra 4 would be.
Lastly, it will be just a huge overall upgrade. It could be thinner, launch on Android 5.0 keylime pie, and have a full HD screen. All of these would make it much better than the current gen Nexus 7. Besides, if you decide the tablet isn't that much of an improvement, you can buy the orignal Nexus 7 for probably a big discount of Ebay.