The normal non-vr versions already solve part of this: The overall size of the world is part of the initial game set up but that doesn't really reveal your position until you manage to uncover an edge in the fog of war. So you wouldn't don't need to change the zoom any, just translate the view to keep it centered as the player discovers new tiles until they discover ones on a boundary which anchors it.

Easy option is to make it a globe then that you could spin around.