Rocksteady have deliberately held back giving us Gotham City. For good reason, you don't obsolete your own product with one massive leap - you slowly make elements of it redundant whilst charging full price for each iteration. See: Gilette razors.
The issue regarding travelling, will be fixed with the Batmobile, Batcycle and Batplane. Already, this is the only action that Rocksteady need to perform to ensure that Gotham City rakes in the sales - but I don't believe they'll stop there.
The true power of the villain - as mentioned in the article - is the unpredictability. Immensely difficult to achieve in a finite resource such as a game, developers don't have the ability to create a seemingly endless set of scenarios for their playerbase, but the playerbase itself does.
Looking at Little Big Planet and to a lesser degree inFamous 2 - the community is extremely willing to essentially build their own game if the developer allows it, both by a robust tool set and an acceptable method of integration.
With Demon Souls/Dark Souls unique "Single player but Multi player" format, it's been proven that players love the idea of encroaching on and being encroached upon by the community, even if they're the sole hero of their world.
With Gotham City, Rocksteady simply need to provide the villains, provide the rules for their behaviours (i.e. Freeze wouldn't be popping down to the steel mill at any time soon) and allow the community to build their own villain scenarios.
Other players can then decide whether they wish for these scenarios to migrate into their world; with filters such as quality, villain focused upon, difficulty, frequency etc.
Whilst playing the game, these scenarios will then appear in your world as seemingly organic actions. Download rates will be fairly low, seeing as you're merely loading actions with assets already on the recipient side.
Not only are we still playing the hero, but we're all also fighting as the villains - potentially creating incredibly devious plots and seeing how well they hold up against the heroes out there.
Like a true villain, we'll fail. But we'll come back, with an even more devious plan than the last.
All this being said though, I truly imagine this will only manifest come Gotham City 2. Still have vehicles to add...