There are quite a lot of DLC incentives coming to Arkham Knight. Be it a retailer exclusive, PlayStation 4 exclusive, pre-order exclusive or Season Pass exclusive, it seems it will be very hard to honestly own all the content from day one.
If you want to play as the Red Hood, for example, you’ll need to buy from GameStop (or Game in the UK). Just for that content, here is a little trailer showing off the character in the game…briefly. Over half of this is a live action morbid joke about the Red Hood killing a lot of people.
But hey! Advertising and stuff.