I think it is too early to say much about the mortality rate. 4% is an upper bound, since that is how many lab confirmed cases have resulted in death, but that doesn't account for all of the minor cases where people didn't even know they had it.
4% might be an upper bound under normal situation when there is sufficient availability of intensive care places. When these places become saturated then % of mortality will approach % of people needing intensive care.
Please also note that many people who require intensive care but survive are left with huge chronic damage to their lungs that will affect their quality of life for the rest of their lives.
