A 3D open world Pokemon game would be absolutely great, but based on pretty much every game in the mainstream Pokemon series... ever, it's not going to happen. (Colosseum was the closest we've ever gotten).
My money is on a new generation of Pokemon, a new region and new gym leaders, and we'll be fighting those gym leaders like we always do in the effort of beating the elite 4 and *insert evil team here*. Extra money if the final evolution of the fire starter is also a fighting type. The graphics will only be a slight improvement over Black and White 2.
The game may or may not have WiiU compatibility.
Typically every generation we see the same formula with only slight changes, and sometimes they even take two steps forward, one step back.
Gen 2 (gold, silver, crystal)---> Day and Night system, gender
Gen 3 (ruby, sapphire, emerald)---> Diving and berry growing, removed the day and night system (makes no sense), added weather effects and a desert.
(Fire) Red and (Leaf) Green remake---> Was anything new actually in this?
Gen 4 (Diamond, Pearl, Platinum)---> Gender differences in Pokemon sprites, swarms, global trade
(Heart) Gold and (Soul) Silver remake---> Partner Pokemon, somewhat 3D (environmental only)
Gen 5 (Black and White, Black 2, White 2)---> Moving Pokemon sprites, somewhat more 3D (environmental only), Dream World (Berry growing is here), removed partner Pokemon...
EDIT: Black and White were the first games in which Zubat was not found in caves, sadly that changed in Black and White 2.
Somewhere they added back in the Day/Night system, although I'm not sure what generation that happened on.
Gen 6 (predictions): No more use of friend codes, somewhat more more 3D (environmental only) (I just don't think Gamefreak will go there all the way). Maybe add partner Pokemon back in.