Not only it will not destroy altcoins it will on contrary make them super expensive as well. People who have seen very few rises and falls like this who are noob on the subject of bitcoin never seen what happens to altcoins back in the day so they assume this is the norm when bitcoin goes up. The real deal is when bitcoin goes up the altcoins lose value in bitcoin but they stay around the same on dollar value and after a while when bitcoin stays high and doesn't move they go up as well.

For example, if bitcoin becomes 100 thousand ethereum will be still around 150 dollar value but the bitcoin value will fall, then when bitcoin stays at 100 thousand for a month or two then ethereum will start to back to what it used to be in bitcoin value which will result with a big increase in dollar value of etheruem. It is always like that, altcoins "follow" bitcoin but bitcoin needs to stay high for a while.