That depends a bit on how the sell is happening.

In the sbdpotato case, they sell steem on a daily basis as a taker (accepting the highest priced buy order), therefore they are actively pushing STEEM price down everyday.

If project hope does the same they are also an active downward force.

The 800k from steem Inc probably aren't sold immediately, and they putting sell orders, acting more as a liquidity provider (I hope they are doing this. Wasn't able to check it yet.)

But in the end is more about volume in on direction or another. Unless there is a movement to give people reason to buy STEEM more than people are selling, the price will be pushed down.

Also there is always steem entering the system due to inflation, so the sell pressure is a constant.

What is needed is good reasons for people to buy STEEM.