I do not think that this can even happen, the bitcoin is so big and the altcoins are still pretty small compared with the bitcoin.
Maybe in the far future that this can happen but I do not really believe in that it can happen if I have to be honest.
I also think it's impossible to replace bitcoin by another crypto currency. Because Bitcoin is in a strong position which can't be break soon.And Bitcoin is giving customer much facilities than other coin, so I don't think its going to happen.
And I doubt there are other cryptos that can have the same experience of what bitcoin has been established.
Bitcoin before reaching it's progress as of today really goes into lots of trials and test. No way other cryptos will be like that since the main is always be the main.