Due to decentralised behaviour, it will exist forever.
It is good to be positive that bitcoin will live longer and continue to be more relevant than what we have at the moment but that it will live forever is what we can't completely say how realistic that sort of thing is... Technologically speaking, the world is growing at a very fast pace and with time, what's technologically relevant today might not be so relevant with time. This is what has paved way for bitcoin because it becomes an answer to the needs the financial system of the world has had need of since the past.
As long as big institutions, whales, and the demand for bitcoin continues to gain momentum, then we can be certain that bitcoin will continue to blossom and grow.