We can spent more times discussing this, but let's fe real here, who expected bitcoin to be created? I found out for this year ago, and before that I didn't even think about something like this can happen.
It's just that anything can happen, I believe in bitcoin don't understand me wrong, I believe bitcoin will last a long time, but I'm opened for new things, and who knows what will happen in 50 years from now, this technology is changing everything each year. In some moments it's very hard to follow that progress, even harder to predict far future.
Yeah you're right there will be no one who knows the future of bitcoin and you know that technology will always change and grow better. bitcoin were present in the 2000's might look old-fashioned in a few years to come, so it is very likely that bitcoin will be replaced by more sophisticated cryptocurrency, this is just my opinion
Something better could always make its way but I don't think tis going to take us by surprise as bitcoin did, since I'm pretty sure when this new hypothetical coin comes there will be a lot of talk here in the forum.