yes it may happen but i think bitcoin has reached to a level where it is difficult for any other cryptocurrency to replace it or reached to its level because it takes a huge time to evolve and bitcoin takes almost 10 year to reached this level. in other words we can say that it is the mother of all cryptocurrency.......
Well, you're right. maybe someday, there will be a coin which is better than the bitcoin, because we will never know, what kind of coins will be developed in the future. but, bitcoin has been at a different level. wherein the level is very difficult to achieve by alrcoin that exist today.