Bitcoin is going 9yrs old, so far no alts surpasses Bitcoin. For 9yrs it remains the king. While Bitcoin is going down, no alts remains strong. All alts are crashing too. This is the best indication that Bitcoin has no replacement.
I agree with that but if you think that Bitcoin will run as the only cryptocurrency I think that's impossible, but due to the fact that Bitcoin contains the best possible feature that a cryptocurrency must have I guess its a long way process for some currency to sprout out of nowhere and imitate or even to be better than this community, but as I have said this is very possible.