Like all digital technology, it is unquestionable that sooner or later bitcoin will have to be replaced by a superior technology, just as in the past we saw many devices become obsolete when at the time seemed insurmountable, such as CDs or PCs.
Obviously this will happen in a gradual way, but I do not believe that bitcoin can retain its current dominance for more than ten years before starting to fall into disuse, although perhaps its influence could persist in the market about ten years.
In the end, bitcoin is likely to subsist for many years, but by then it will have evolved in such a way that it will be virtually unrecognizable for todays standards, and in fact it is difficult that in 15 years there is something similar to the current cryptocurrencies before the spectacular advances in digital technology that are approaching.
Even though nothing lasts forever, and something new will replace the current technology we can still use, love and support Bitcoin as it is the pioneering coin. It brings life to Altcoins that is why Alts are pretty dependent to Bitcoin in terms of price flow on the market. Altcoins are new and there are even hundreds created every single day but where are they now? What I mean is those new advanced and improved technologies are still following Bitcoin's track.