It is possible for some alt coin to cross the market cap on bitcoin in  future. But that will not reduce the importance and value of bitcoin. When we talk about crypto, first thing that comes in mind of 99% people is bitcoin.

So far as the survival of alt coins is concerned, some alt coins will do well. Like BAT for example , it is related to Brave browser and I really like the integration of Brave and Bat coin. Getting rewarded for using a browser plus the browser has many other use cases like no ads while browsing YouTube videos. What more can a user ask for ?