Unlikely to live up to expectations.
Eidos hasn't produced anything particularly noteworthy recently, far as I'm aware; likely none of the team from the original games will be working on it, Eidos and the associated publisher (Square Enix isn't it?) has shareholders to please, no-kill stealth gameplay with open ended environments is a niche, and niches don't please shareholders.
System Shock 2 fans didn't like Bioshock, X-Com fans don't like the XCOM reboot (far as I'm aware anyway, I liked both), and Thief fans are unlikely to like this.
It's a shift in the times. I don't like beating the 'it was better yesterday' drum, I hate that fuckin' drum, but even Dishonored - far as I'm aware a moderately successful game - was niche, and probably didn't prove to publishers that such a game can be successful enough to please shareholders. I 'unno, depends on kind of the budget it has and the kind of investment it has behind it.
At least there's Dishonored. I love Dishonored. I'm in the minority, apparently, but GOD I love it. Off topic I know.
I think what I'm trying to say is that it's not in Eidos' best interests as a business to make a Thief reboot that's entirely in the spirit of the original game. Guess we just have to hope on their interests as a game developer.