Right now, bitcoin is on the top, number 1, it's obvious.
Bitcoin already have very strong foundation, many users, merchants, even bitcoin ATM, debit cards, many exchangers accept bitcoin etc.
All this is fine but in the Internet world it's very difficult to predict future, next 5, 10 or 20 years.
Do you remember Nokia, or AOL, for example?
They was industry leaders, but more advanced technology, smartphones and Google replaced them.
So, if something better comes, it will replace bitcoin.
We don't know yet what may happen in the future.
I think nokia is losing competitiveness because they are not doing any innovation than its competitors. But bitcoin will continue to evolve and innovate that's why bitcoin will persist