Interesting idea.
I don't think people are powering-down because they want out. They do it, because they can't freely sell. But they could rebuy at any time if they powered down, so the best thing to do if one holds a lot of SP is to power down ASAP. Everyone wants the forbidden fruit.
For this same reason i haven't bought any steem yet. Why should i ? If i bought, the first thing i'd do with them is to power-down. I'm going to wait for the powerdowns and inflation to do its works, and then when/if steem breaks out of it's downtrend i'll buy.