That's just the thing, if its the same map, will it even feel like a new game, or just BOTW DLC Pack 3, just at $60?
1. Hyrule Castle is being raised, maybe other structures get raised too like the towers did in BotW 1.
2. They found Ganondorf underground in an ancient dungeon like place. Who's to say we may have more of those. So tons of underground hyrule.
3. Hyrule Castle is being raised, maybe we visit Skyloft and other places in the sky?
4. Maybe its been a few years since BotW finished and thus many new towns, ruins fixed, Lon Lon ranch rebuilt, ect. The world could look insanely different being not broken. Remember, enemies spread throughout the world, closest to hyrule town kept all civs like spread out to the edges.
5. Think of OoT and the difference between adult and young Link's hyrule. Same overworld, yet very different.
6. 90% of all Zelda games take place in the same Hyrule. Always going to Zora's domain, death mountain, gerudu's desert, ect. All in same locations. Does it looking somewhat different in each game really make it feel so much more special? I'm more of a different mind many times. I'm like comparing Zora's domain in each game and like "how does it look so insanely different each time" Not that things can't change, but sometimes the locations seem almost different or there is no evidence of what it used to be.
7. I feel like will not have his rune abilities he had in BotW, thus even if exactly the same world it will feel totally different traversing it.