Are you just guessing, or is it a fact that people are powering down? I have not heard anything about that...If it is a fact, then you are right, there will be some extra pressure in STEEM price, but then again, that would be nice for the people who wants to power up!!
Powering down is happening, but the problem will not be seen immediately as it takes 13 weeks to power down completely. Of course this could be changed if some people put in a lot of money in Steem but I don't see this happening right now, all the money is going to BTC, and it will continue this way until after the hard fork and then we should be seeing a change in investors choices, hopefully Steem will seem like a good idea to a few investors with a lot of cash.
It's the people with the big bucks who make the trends minnows just follow hoping to make some money.