I don't think bitcoin is replaceable with any altcoin although it's transactions time getting slower but still people feel confident with bitcoins more and why not it's the first decentralized digital currency and survived for over 9 years with lot of bad news, government regulations etc. Bitcoin will always stay on top.
I cannot clearly see it happening because bitcoin is already distinguished as the King of all cryptocurrencies aince bitcoin ia the only cryptocurrency that reached $20000 mark. The first thing for an alternative coin to have is a great potential to the market and huge demand although everything has a possibility, the feasibility of an altcoin to replace bitcoin is unpredictable.
