B&H has the Rokinon 16mm f/2.0 ED AS UMC CS Lens available for preorder.
The Samyang/Rokinon Tilt-Shift 24mm f/3.5 ED AS UMC Lens is availabe for preorder at the following retailers:
Samyang Tilt-Shift 24mm f/3.5 ED AS UMC Lens - B&H | Adorama
Rokinon Tilt-Shift 24mm f/3.5 ED AS UMC Lens - B&H | Adorama | Amazon