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?
Yes, absolutely. But likely not for several years. Bitcoin was the first blockchain and the first cryptocurrency. Like any first entry in a new technology market it will in time be surpassed by others that improve upon it's ideas. Ethereum will almost definitely be the next top blockchain coin and will likely remain in the top spot for a long time. And whatever passes Ethereum probably doesn't exist yet. Maybe Waves will third coin after bitcoin and Ethereum