Whilst it is believable that a system like Bitcoin could have a market cap that supports a BTC price of $100k, how do we know that a different system won't take

Whilst it is believable that a system like Bitcoin could have a market cap that supports a BTC price of $100k, how do we know that a different system won't take its place before it does? Bitcoin is in a strong position as it is first to the market but I think something similar could easily take its place if it was considerably better technically. Whether this will be a totally different system or a Bitcoin 1.1 that can be migrated to, I don't know. You could have said that the total market for IRC is 7bn people using it every day but now there are more people using other systems like Facebook Messenger.