Not open world. At least for next few games.
Nor heavily story driven. Zelda games doesn't get developed around a story, but story gets developed around gameplay.
The core of a Zelda is exploration, dungeons and their clever puzzles.
I think next game will have to do something with next Switch's gimmick, if there is any.
They used the mix/match/craft concept already for TOTK. Physics for the BOTW... Ability changes for the recent Zelda one...
I think something other than those types would be key new feature - or combination of all of them.
Maybe it would be something about woodworking/stone carving/blacksmithing while collecting materials - that you create your own weapons?
Not as ultrahand, but more of condensed, more concise and infinitely different types of weapons that can really creative - and can be used to solve the puzzles...
But the art style wise - don't know. I doubt if they'll release SD/Chibi style for their mainline 3D zelda now - I think it will stay as 3d cell shaded look (which I don't mind, provided with excellent animations)