Other cryptocurrency are just a way to get bitcoin , because bitcoin became hard to mine and expensive to buy people thought that mining other coins like doge coin and altcoin will be more efficient than just wasting time trying to get bitcoin , the there is a possibility that bitcoin will be replaced by another cryptocurrency but that will not be the case for a long time.
You definitely does not get it, bitcoin is not expensive because it's literally not a produce where we purchase low but sells it very expensive, it's the demand that is making the price big and that is good because the bigger the price it's more valuable.And as the demand gets higher, there is no way that bitcoin will be replaced by another crypto currency. As a matter of fact, many miners of alt coins are looking forward to sell immediately their mined alt coins because that is going to give them more advantage to hold their profit from selling all their mined alt coins.
We really can't predict future, what may happen in 20, 30 or 50 years.
Internet became famous just 15 years ago, smartphones in last 5, 6 years.
Bitcoin? Only in last 4-5 years.
Right now, Bitcoin is obviously the most famous virtual currency and its price is slowly going up but this can change any moment.
Someone can create even more popular virtual currency, it's possible.
Of course, if such scenario, out of habit, still many people will continue to use Bitcoin but less than before.
We really can't know what future will brings us
