After doing some research, it turns out that this is a very important question. Specifically, there is a strong inverse relationship between the magnitude of short-term VIX reversion and the continued strength of the longer-term mean reversion trend. Said another way: if the VIX snaps back dramatically in a couple of days, it is more likely that echo volatility (VIX aftershocks, if you prefer) will be an important factor in the next few weeks.
On the one hand, this should not come as a surprise: if most of the mean reversion happens in a couple of days, then less of that same mean-reverting move remains for later. On the other hand, my research suggests that you can use the magnitude of the short-term mean reversion move to measure the magnitude of the long-term mean reversion with surprising accuracy – at least with the benefit of 20-20 hindsight. Whether the future will mirror the past remains to be seen.
Of course, the larger question involves expanding the implications of this finding from the VIX world to the world of the SPX and the broader markets. In this arena, the data look to be encouraging as well.
Arrow up on the predictive value of the VIX for the broader markets.