I really really want something like Join Avenue to return.
Absolutely LOVED that feature in White/Black 2. (Maybe an extension of this: a mall of some sort? Or just the Join Avenue continued...)
It's an interesting move towards the 'tid-bit' styled game play like many phone games. (Where you can do a little every day - giving you a reason to visit every so often.)
As such, I really liked the feature (forget which gen/game) where you could change the bottom screen to different things. (Like a watch, daycare monitor, map...)
Hmmm. Customization would be AWESOME. Especially if they decide to do something neat like having similar clothing parts to previous characters in the series allowing us to mix and match! Maybe even unlocking gym leader/certain trainer 'styles' after beating them along the way. Maybe even pokemon 'themed' items (either colour scheme or otherwise). So many delightful possibilities...