We cant realy predict how long bitcoin will be the number 1 in crypto currency world and i dont think there is some new coins will be made in the future that can beat bitcoin. Even etherium also is a very popular crypto currency and tip 2 in the market he is still way too far on the bitcoin price.
Yes i agree, we cant predict if when bitcoin become #1 currency because of our new technology and smart people we dont know if there will come a new and good coin than bitcoin that will beat to become a #1 currency. We dont know the future, maybe someday bitcoin will be the #1 currency and we hope that it happens because its better to use.