I had previously doubted that Bitcoin would be replaced by another currency. But my mind has changed. Because I see there are many other cryptocurrencies that the developers are trying hard to solve the problems in cryptocurrencies. What about bitcoin? We don't know who are the developers and no effort is being made to develop it.
If you don't try hard, your rivals will win. Bitcoin's rivals will win too.
Bitcoin is the leading altcoin and it is leading others with poles. Yes there are issues with bitcoin which the others are also having. I believe the developers of bitcoin are not sleeping they are also aware of these issues and the challenge posed by the advancing altcoins so they will be working to maintain their position.
I think users don't have to worry about it, bitcoin is much better known than altcoin, so people will be more familiar and will first use bitcoin than altcoin, you're right that the competition will get tighter in the future, but bitcoin developers certainly will not sleep, they will keep on bitcoin position