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's impossible in my opinion, Bitcoin being obsoleted and to be no more used. There are other coins namely altcoins that has potential with a high rate of the increase of their market value but Bitcoin has a large community that generates a high market demand. And that I think, is its biggest weapon for it to be more succesful on the next years to come.
It could be but that cryptocurrency must probably have a different technology better than the blockchain and present better features than the bitcoin forks around or so called altcoins. I don't think they can really compete well against the bitcoin if they aren't innovative enough to draw a lot of the bitcoin market volume away.