Photoshop supports the following 3d file formats for the export:
These file formats are supported by most of the 3D computer graphics programs
like 3D Studio Max, Cinema 4D, zBrush, Blender or Maya.
Creating real 3D maps is a huge advantage over the Terrain generator when it comes to change maps afterwards. Thus it is also possible to print the map as a 3D object. If there is no 3D printer at your disposal, you can also use an online service for 3D printing or a local shop.