You cannot just predict a dump by looking at someone moving their coins to an exchange. There are other possibilities too, like selling them for their own profit or may be the previous exchange was not preferable to them. Anyways, we cannot do anything about it right now rather than observing the situation.
That's how speculation works. There really aren't any tried and tested methods to predict how the Bitcoin market will move, so people try to look for anything and everything they can use. A move like this
could actually be significant depending on the context (like Roger Ver moving 25k coins to an exchange last November lol), but this one obviously isn't. This mentality about whales being able to freely control the market has become a self-fulfilling prophecy where we allow them to affect the market simply by moving their coins.