Would a new Thief game even matter? Honest question.
Thief was a revolution because of its technology and how it stressed subtly and stealth over run-and-gun. Did it otherwise simply have good design? Yes, but that's besides the point. Stealth mechanics and the technology that makes it possible no longer push the envelope and hasn't for 20 years. Outside of marketing, what's the big deal about Thief in 2025?
Unfortunately a new Thief game would most likely be a commerial failure. It appeals to a tiny niche of gamers who values patience and caution. Beside the classic stealth mechanic, it would require top notch ambiance, soundtrack, voice acting and writing. Make it an investigation game revolving around mysteries, power plays, secrets... That's why I still enjoy Deadly Shadows even now, despite its numerous flaws.
Then I remember the year is 2025, and interns no longer run game companies. So yeah, rather nuThief 2.