Does the whale digger really sold all his CLAMs yesterday?
If you believe what he says, yes. Beyond that it is impossible to know.
No more dumps?
Other people, including whoever supposedly bought his 100 BTC worth of CLAMs, might dump.
The stake weight on the network has gone up by about 200K CLAMs, so someone is staking coins that weren't be staked yesterday. That is unambiguous.
There was another 50 bitcoin dump about twelve hours after the whale digger said he'd run out of CLAMS. Either he was lying or someone else who bought in low was taking profits. CLAMS had the biggest price swings of any coin yesterday, and that could have drawn speculators to the market looking for a fast profit.