The new Apple TV will support third-party game controllers in in its attempt to bring iOS-style gaming to the living room - but developers can't make those controllers a requirement.
In a programming guide for Apple's new tvOS platform, the company notes that every game developed for the Apple TV is required to support the touchpad-enabled Siri remote.
This new requirement could significantly change the kinds of games developers are able to target for the new system - the new Siri remote is certainly more capable than the one it is replacing, but it's still not the ideal game controller.