Terraria is, at its core, a 2-D sandbox game.
Removing the 2 dimensionality would, in my mind, make it feel a lot less original.
Besides the collective nightmares that would be Wiring, any sort of teleportation, maps, etc. how would this improve the game in any way?
If you really want a 3-D sandbox adventure game, I’m pretty sure there’s one owned by Microsoft? Something about a Cave Game?