I don't know when bitcoin is disappear or replace but I think the bitcoin is not forever because no forever. Like said the teenagers because they are hurt by their boyfriend or girlfriend. For me, the bitcoin is not forever, the other bitcoiners taking advantage because other countries against bitcoin they think that the other countries destroy the bitcoin so they sell account to earned more money.
Bitcoin can be replace or disappear any time because anything can happen. There is no permanent in this world that last forever but as of now bitcoin is having a good performance in crypto currency, I'm also enjoying the peak of bitcoin.