iPhone 5S will be made as much from gold, as the original iPhone 5 is made from silver.
The 128 GB option seems pretty obvious.
Every “S” iPhone has upped the storage capacity over its non-S variant:
The 3G was available with 8 or 16 GB. The 3GS added 32GB.
The iPhone 4 was available with 8, 16 or 32 GB–the 4S dropped the 8GB option and added a 64 GB version.
The iPhone 5 is available in 16, 32 and 64 GB–so it would follow logically that the 5S would add a 128 GB version (and possibly even drop the 16 GB option, leaving that as an iPhone 5-only option moving forward).