Personally I don't think it will affect it all that much.. But I don't get why everything has to be open world nowadays. In any case I hope that these "bread crumbs" can be turned off (the red line, not the colored objects). Whenever there's this guiding line in a game you just follow it like a zombie and rush through the…
I liked Mirrors Edge because it felt like it had 2 play styles due to it's linear levels. First time through was problem solving and testing the mechanics, each additional run through a level was about how fast or fun can I run through this area. I think having it open world will kill that.
I'm not too concerned about the realism of the city, to be honest. Far too many of the recent AC games have been more interested in building a world than building a fun environment to play with mechanics in. If ME is going to be open world, I'd be much happier with a map that provides great play and emergent experiences…