Rock Racoon alternative for Apple TV 2?

Is there a way to make a tethered jailbreak untethered on the latest Apple TV firmware without having to wipe out all the files and starting from scratch?

No unfortunately not.

It would be great if there was a way to do it without destroying all files.

I copy my XBMC folder, so I don’t have to reinstall everything every time. Then just put the folder back in as soon as I install XBMC again. Works great!

No! There is no way to make a tethered jailbreak untethered on the latest Apple TV
firmware without losing all files.