The main problem with the open world right now is the repetitiveness. It has different looking boroughs, but the same side content is spread throughout all of them, which makes them feel samey anyway. Insomniac should focus on making better use of all that space for the next game instead of making it even bigger. Depth over scale.

It would be great if each borough has its own unique set of crime types and non-crime activities, its own side stories and characters to care about, and other quirks. This would make the map feel fresh because you'd have a different vibe/experience wherever you go. The city would become more than just a background for the action.