Just to play the devil here, wasn't Zelda pretty much "open world" from the get-go? The first game started you weapon less and you had to meander about to find the levels. It wasn't a gargantuan world by today's standards nor did it have all the little side tasks, yet one could still consider it "open world".

I WILL say that modern Zeldas are getting a little long in the tooth to finish. Twilight Princess I just wanted it to end when I got close to finishing it. It felt like the puzzles and traveling was there just to extend the game. Skyward Sword just seems to make you revisit dungeons (not in a good way-OoT played this out better) and go through that stupid spirit world to collect shinies, which was ripped right out of TP and was the least thing I liked.