I always thought that xK30/60/120fps were for slow mo in post production... or at least that is my usage but I am not a serious videographer. What scenarios would you want audio as well?
I'm no videographer yet. For me it'd be for slow mo rifle/pistol range at work. Working parts slapping forward and bangs in slow motion produce great results. I admit it's niche and not many folks would require it, but I can hope for audio in 1080 @120p at least.