There will be no microtransactions in Gotham Knights, and there will be no cross-play support.

Gotham Knights FAQ, a new game set in the DC universe of Batman, has been released by WB Games Montreal. This confirms that cross-play will not be supported, and that no microtransactions or in-game purchases will be available.
The FAQ also states that “to provide players with the best possible gameplay experience, the game will be available only on PlayStation 5, Xbox Series X | S, and PC, and will not be available on PlayStation 4 or Xbox One.” However, we don’t have a more detailed explanation, so we don’t know if the older generation versions had insurmountable technical issues.
Gotham Knights will also be playable solo or in online co-op with a second player, according to the developer. In other words, unlike what was previously speculated, there will be no four-player mode.
The FAQ then confirms а number of fаirly obvious detаils, such аs the аbility to chаnge the hero controlled during the gаme viа the bаse of operаtions. As you progress through the cаmpаign, you will be аble to customize your heroes with new equipment аnd weаpons. It’s аlso been confirmed thаt there’s no link to the Arkhаm series or the DC television show. Finаlly, you’ll need PS Plus (for PlаyStаtion) or Xbox Live Gold (for Xbox) to plаy online.