In the latest Sonic Talk 670 Jamie Lidell talks about a 100 KHz microphone and digital microphone interface.
As Jamie points out another use for recording above 20 KHz is that you will hear a more realistic sound when you shift a sound down pitch. He pitched down the crunching of table salt, as for instance.
Another thing cool about the Sound Devices audio recorder interface beyond its frequency range is that it records in 32 bit floating point format which gives a very large dynamic range and more protection from digital clipping.
So these together could make an audio quality option that would go moderately high into ultrasonics.