This trailer looks quite nice, but after looking at all the GameInformer articles and interview videos, the bit about being able to explore the breadth of Gotham City sounds iffy.
The interview vid with the art director only mentions AC and never Gotham, and only in a context of them basically putting window dressing on Rocksteady's map to make it look different. Then there's the fact that this team doesn't appear to have anywhere near the experience or expertise that Rocksteady does. The only game mentioned that any of them were involved with was an Incredible Hulk game the creative director worked on that came out in 2005.
I've always wanted to be able to explore Gotham City, and had hoped the franchise would eventually go there, but it seems like a lot for this team to handle. Sure they have access to Rocksteady's input, but that's not the same as hands on experience. Rocksteady had performance issue just with the AC map, and Gotham is much bigger. I get the feeling if we are going to be able to play in Gotham City, it will be somewhat limited.
So I have hopes for this game being good, but I can't help but be skeptical.