Should the game traditionally have an endgame? Or is this intended to be more of a explorable environment? Case and point, should it have some overarching objective, like finding ticket peices for a trainride perhaps? *wink wink*
well, cosmo says it must be the city. That's it. Me and the team im with are adding an endgame point. It is not necessary but just think about what you want your game to be and the audience you want to hit. Some people differ on the way they like open world games or city style games. If you want an endgame point then add one. If not, then don't. Make it however you want. Sorry, I know I am not cosmo but I am saying this by what I've read.
It's up to you, @Rearskyy. Players' mileage may vary on how much they like an 'open' vs 'closed' experience. Strangethink, for example, does a lot of powerful work with games that don't end. Same for Connor Sherlock. But I always like having my games end, or at least reach some sort of milestone.
I'd say that as long as it's true to how you feel about the game and your intentions, that truth will shine through and players will respect whatever choice you make.