That seems a bit strange since the wireless controllers are at the heart of the 360 system. Are you sure that MS isn't just upgrading the wireless controller to a newer model (or maybe just changing the part number for some reason)? See if you can find out more from your source. Discontinuing the controllers doesn't make sense to me.
Maybe MS is coming out with a motion based controller with a real gunsight that could convert to a skateboard, a steering wheel, a broad sword, bow and arrow,etc. Of course it will be wireless. U wouldn't want to hack off the wire with ur broadsword!