Yeah because these people think that bitcoin will die so quick from a new coin or plan or whatever but what they don't know is that the bitcoin has such a big foundation that it's impossible to just swoop away. It would take hell of alot to kill bitcoin that instantly.
We cant really say that theres no altcoin could able to replace bitcoin because we wont know the future yet but as we can see on the situation and issues there are lots of alts which are trying to surpass bitcoin in anyway but still they have failed because bitcoins had already established its pace and isnt easy for it to be destroyed soo easily.
Bitcoin is the king of crypto currency and it won't be easy for any altcoin to replace it as bitcoin holds more number of users in compare to other cryptos and people have more faith in it.
Yeah and the main reason is that it also holds multiple benefits and features with it which is missing in altcoins and that is the reason people will never switch to any other coin from where they are getting limited benefits.
Price may fall down in future but it will never disappear and even if it falls down it has an ability to rise again and go to higher price and it has successfully proved it in the past.