I think that is really the question to ask after VZZ dropped below $10, triggering automatic termination. The prime suspect is TVIZ index that is also a 2 X version of Mid-Term VIX Futures Index, although unlike VZZ it is rebalanced daily. While VZZ is (was) issued by Barclays, TVIZ is from VelocityShares (Credit Suisse). I searched for any info on termination in the prospectus and product page, but could not find an automatic termination clause (Note that all VelocityShares ETFs share the same prospectus)
Vance at Six Figure Investing already covered the topic of termination in great detail on IVO and XIV ETFs. The only thing that I may add is that looking at the list of volatility-related products it does not appear that any of them are in the immediate danger of termination. VelocityShares are rebalanced daily and do not seem to include automatic termination clause. Short volatility ETFs that do have "acceleration" are probably safe, unless we see a major major market disruption event.