The only thing that could possibly get me to upgrade from my 2013 is if they do a Nexus 8. I almost got the G-Pad 8.3 GPe (still not real sure why I didn't). I prefer a 7" tablet to a 10" tablet, but 8" is my sweet spot.
Things that would be nice to have, but won't get me to upgrade on their own (beyond the typical processor, gpu, etc.):
Wireless AC
Innovative camera software/hardware
More color options
64/128 GB options
Front facing speakers
Also, please let the Nexus with an SD nonsense die. It. Will. Not. Happen. Stop asking. Stop saying its on your wishlist. Apple will put an SD in an iPhone before Google adds SD back to a Nexus. Internal storage is the way to go. SD cards do nothing but cause problems.