iOS, iPadOS, and tvOS gain DualShock 4 and Xbox One S (the regular xbox one controller does not have a bluetooth chip) controller support this fall. According to Apple's official document describing the features added with iOS 13 support for PlayStation 4 and Xbox One S controllers will be added in the coming update.
The same is true for tvOS, which will receive support for Playstation 4 and Xbox One S controllers as well.
This means that the announced streaming/link apps like Steam Link, PlayStation Now, Remote Play, and xCloud will be compatible with these controllers.
It seems like the controllers will be integrated in the MFi controller API, that means that all games that support MFi controllers now will support the Playstation 4 and Xbox One S controllers as well. No patching from game devs needed. (Apart from maybe adding additional controls for the clickable thumb sticks aka. R3 and L3)