Bitcoin is long lasting and it is possible that may be another coin will take place of it but not possible in near future,People interest in Bitcoin increasing and its investor ratio also increasing now a days Bitcoin is most profit oriented coin.
It is history that things can be replaced by people according to their need and demand they diver another to leave existing one.
People will lose interest when they are not happy any more on what they are doing. People lose interest because they bored on what they doing. Many people is like this. But bitcoin people are not losing their interest.