Exactly...
The new money on the market goes first to bitcoin, then to ether and the other larger altcoins on the market... then it migrates to smaller coins... there is still time to buy some "good" coins at a bargain.
It goes in a way as those who bought Bitcoin during the Big DIP will definitely want to sell after Bitcoin making a new All Time High, not all may sell so quickly but majority. Them selling and taking their profit is for them to quickly invest into different Altcoins this will help pump this Altcoins. This is why most people are now beginning to invest in this smaller Altcoins.
Maybe it could be like that, but it could be that traders have other concepts, such as they will continue to spend the funds they have to buy BTC while waiting for the maximum price when the halving occurs.