Does it make sense to believe that Bitcoin could one day be replaced by another cryptocurrency, that is, a cryptocurrency that really does make Bitcoin obsolete?
That can totally happen. Nothing is last forever. But I don't think that's an end too soon for bitcoin.
Like you said, it can totally happen but the chances of it are very slim. Bitcoin now reigns as the number one cryptocurrency despite the growing number of competitors in the market due to its high price and usage. Another thing, millions of people are already investing into bitcoin and its popularity has already been noticed around the world. Some countries even ban the usage of bitcoins due to its nature being decentralized, thus making it difficult to regulate. Well, no one knows what will happen in the future but I really doubt that bitcoin will be replaced soon.