From the top, there are three ways to talk to an Apple TV (at a 50,000 foot level):
IR: Apple does not offer keyboard functionality via IR. Nothing we can do here.
IP: Apple has encrypted communications over this interface. We are not aware of a way around this. Nobody else has ever gotten past this either.
Bluetooth: Apple does not allow apps to use Bluetooth. (Actually the answer is a bit more complex than that but not really.)
So, if there is a hope for an Apple TV keyboard, it will be via IP either because Apple opens it up like they did with Apple TV V1, or because we or someone else finds a way to authenticate to it properly.