My suggestion, as usual, is a Basilisk question.
And in light of recent events, it might be interesting to factor the cryonics survey question into two: whether cryonics works in principle, and whether cryonics as currently practiced by ALCOR/CI will work.
Given that it's been a while since the last survey (http://lesswrong.com/lw/lhg/2014_survey_results/)
It's now time to open the floor to suggestions of improvements to the last survey. If you have a question you think should be on the survey (perhaps with reasons why, predictions as to the result, or other useful commentary about a survey question)
Alternatively questions that should not be included in the next survey, with similar reasons as to why...
survey is now up (2016-03-26) http://lesswrong.com/lw/nfk/lesswrong_2016_survey/