It looks like: "Filters in Camera" and "AirDrop" are the only 2 iOS 7 features that are absent on the iPhone 4S. Obviously, the 4S won't be able to do hardware required features like the TouchID and some of the new camera features that the 5s is capable of because of its upgraded hardware.
It's kind of like NFC. You can transfer files like pictures, contacts, etc. between iOS devices, but without having to tap devices. It's a feature that's on the Mac too.
It looks like: "Filters in Camera" and "AirDrop" are the only 2 iOS 7 features that are absent on the iPhone 4S. Obviously, the 4S won't be able to do hardware required features like the TouchID and some of the new camera features that the 5s is capable of because of its upgraded hardware.