"Exact same"? That's a colossal assumption. A company the size of Nintendo will absolutely make improvements to the new iteration of the engine - some clearly noticeable to players, some not. Thinking back historically, many game series used the "same" engine. Quake 1/2/3, Halo 1/2/3, Command & Conquer / Red Alert, Witcher 2/3/Cyberpunk2077, Elder Scrolls 3/4/5/Fallout3/NV/4 and so on (too lazy to think of more). Further, think of how many games are made with Unity, Unreal Engine, etc. Yet further, check the credits list of Breath of the Wild -- they absolutely have the workforce to make serious changes to the engine and work on a compelling new game in concert: https://www.mobygames.com/game/switch/legend-of-zelda-breath...