S5 wire less capability
Fuji is already talking about a different battery in the S5 than
the D200. If this is the case, then the wireless transmitter for
the D200 may not work on the S5.
Maybe, maybe not. The WT-3 simply passes the same three power connections on. So if Fujifilm has only changed the battery but not the connections (which would be strange if they did--that's a deep engineering change), then I'd guess that it could be done.
It's very possible we will need two different transmitters, one for
the Nikon and one for the S5?
Possible. Fujifilm was showing their own WiFi accessory for some of their cameras at Photokina. On the flip side, the specific statement in their early literature talks about wired and unwired network connections, which exactly mimics the early WT-3 marketing materials.
author, Nikon Field Guide & Nikon Flash Guide
editor, Nikon DSLR Report
author, Complete Guides: D50, D70, D100, D200, D1 series, D2h, D2x, S2 Pro