I had previously doubted that Bitcoin would be replaced by another currency. But my mind has changed. Because I see there are many other cryptocurrencies that the developers are trying hard to solve the problems in cryptocurrencies. What about bitcoin? We don't know who are the developers and no effort is being made to develop it.
If you don't try hard, your rivals will win. Bitcoin's rivals will win too.
When bitcoin will no longer considered the most profitable investment (Which is the real reason for its high demand) It could end up being replaced by another currency, but while this possibility continues to exist, bitcoin will remain the main cryptocurrency.