Dhruin
SasqWatch
Industrious folks on the NeoGAF forums have been combing through Eidos Montreal jobs looking for hints in Thief 4. Based on the position requirements, they have good evidence that Thief 4 will use the Unreal 3 engine (no suprise) but will also have some sort of mutiplayer or online component. Examples include a job for an "online programmer" who will be "involved in many aspects such as networking, gameplay, debugging, online and offline tools on Thief 4".
More information.
More information.