There was a video with Turn 10 that talked about new accessories for Forza.
They have a whole new system for force feedback. Instead of telling the accessory how to handle the force feedback, they send it a bunch of statistics on acceleration, g-force, braking, etc. Then, the accessory developers can used these statistics and pump them into their own equations in real time to determine how to handle the force feedback, giving it a much more realistic and dynamic feel.
Because of the differences, and of course the existing compatibility issues with the old and new controllers, old accessories will NEVER work with the Xbox One.
They have confirmed that Fanatec will be working on a new range of accessories to utilize the new force feedback system and the accessories will be better than ever. I guess in reality, you don't want your old wheel. They just won't be anything good compared to what the new accessories are capable of.