Steve makes a very good point too - audio buffers aren't really dynamic, they are a fixed size for any given sample rate: the higher the sample rate, the bigger each audio buffer needs to be, and the slower the tempo the bigger the audio buffer gets. Changing the samplerate during playback would change the buffer size (so they are dynamic in that sense) but this would affect a whole load of shizzle, such as information held in buffers for anything requiring delay (delay, chorus, reverb etc) as reducing the samplerate would have to either flush or truncate the buffer. Either way, it can't do it a) gracefully, b) without the listerner noticing it, and most likely c) without BSODding the audio driver.
It's not merely a case of 96 downgrading to 88, either, as actually that wouldn't make a whole heap of difference in DSP, so such a fallback would need at least 48 as well to actually get any significant benefit. It would need to be able to run at least three static buffer sizes at those three samplerates concurrently.
So, which audio cards support three samplerates simultaneously?