Will bitcoin last forever?
We see that's some of the cryptocurrencies ranking level are decreased such as dogecoin before it was ranked #4 but currently I think it doesn't listed even in top #10 ranking... So can bitcoin also decrease its rank in the future or it will remain #1 rank forever?.
Nothing last forever. You are focusing on the cryptocurencies, but you can look further. Nothing stays rank.1 forever. If you look last 5000 years timeline China was strongest country for most of the rime. And where was China last 500 years? Spain, Netherlands, UK and USA were Nr.1.