Big fan of canon DSLR's , I am always surprised that why canon is not introducing the voice in 120fps. whereas all SONY cameras have 120fps with voice recording. so that as per need in editing I can use voice are can covert it into slow motion.
Generally audio is recorded separately with better mics and audio equipment and mixed in during the editing process, I'm not sure that Canon was worried about users that want to do more higher end video work using the on camera audio.