Assuming all the pics we've seen aren't bullshots, there's no way a current gen console or the Wii U (which is more or less a current gen console) could handle that level of detail.

Though I think a lot of people are expecting the next gen of console games to blow them away like the PS1 to PS2 did, or PS2 to PS3 are in for a bit of a disappointment. We're starting to approach the point of diminishing returns in graphical quality. While there's plenty of room for improvements, it's going to be drilling down into finer and less noticeable details. Mostly, it'll be about maintaining roughly the same level of graphics while bringing more of the world itself alive.

For example, while playing through Skyrim, I found myself in a scene where I had to help protect a city under siege.

...and that siege was about 12 guys rushing up a hill at me while some huge battle apparently took place offscreen. It was kinda disappointing, but it was really all the 360 and PS3 could handle at that level of detail. The next generation of consoles will likely have slightly better graphics, but will mostly impress you by slapping you right in the middle of an actual huge battle filled with thousands of little characters running around chopping at each other.

It'll probably be about the same thing with Thief. The graphics will be slightly better than what you'd get on the PS3/360/blah, but it could have The City filled with tons of people walking around on the streets and alleyways doing their thing. The few screenshots we've already seen kinda point towards that.