I can’t believe how much time has passed between Arkham Knight.
Hopefully they do something fresh with the new game and take it to another level.
I think there's plenty they can do to make it feel fresh. Maybe the tech isn't there (although maybe if it's for next gen) but I'd love a living and breathing Gotham City, with citizens going about their lives - instead of it only being populated by criminals. And while it's great being Batman, I'd quite like them to get rid of the 'one night' idea and have a storyline taking place over a few days or weeks, with the ability to do some non-Batman stuff during the day. Think it'd be fun playing as Bruce and having to do some intel gathering during the day before donning the cape and following up on the lead at night.
I'd also like to see more use of wider DC characters. After four games, there's not a ton of fresh faces from Batman's rogues gallery - they've already made extensive use of Joker, Catwoman, Penguin, Two Face, Riddler, Scarecrow, Ra's, Harley Quinn, Hush, Clayface, Mr Freeze, Poison Ivy, Bane, Deathstroke, Deadshot, Mad Hatter, Killer Croc, Firefly, Hugo Strange, Zsasz, Black Mask and Red Hood. Plus a few more smaller villains.
But there's plenty of recognisable baddies usually associated with other heroes who would be a great fit. Lex Luthor in particular, as he's a great parallel to Bruce Wayne. You could have Bruce visit Metropolis for a few chapters, with potential for a Superman cameo. And you could have the Suicide Squad being sent to kill Batman by Amanda Waller, and fill the team up with loads of villains who normally wouldn't be found in Gotham. Court of Owls seem nailed on to be a big part of the next game so between them, the Suicide Squad and Lex, you've got a really fresh line up of opponents - and obviously there'd still be loads of scope to fit in villains we'd already seen.