Several CVs for Eidos employees (uncovered on NeoGAF) seem to suggest that the upcoming Thief 4 will feature some sort of an online mode.
Most telling is this employee’s LinkedIn profile which states: “Involved in many aspects such as networking, gameplay, debugging, online and offline tools on Thief 4.”
Could this mean multiplayer is in store for the sequel or something different? Leaderboards perhaps?
Also mentioned is the use of Unreal Engine, which could well power the game.
Still, we’d like to actually see the game at this point instead of speculation.