No, we don't know for sure, but the 60+% are the current estimate based on the data available. The rates are not so much dependant on how "deadly" a disease is,

No, we don't know for sure, but the 60+% are the current estimate based on the data available. The rates are not so much dependant on how "deadly" a disease is, but on how long you don't know you have the disease before you get noticeably sick. And there Covid-19 is so nasty. As far as we know, one is infectious for some time before (if ever) you get sick. On the other side, those who do get sick, get so badly.