No because you don’t know how many of them will die. In your definition you know the R not the F. Look, I’m quoting the WHO report. You’re welcome to take it up with them.
Case fatality rate is defined as the fatality rate of known cases. You can’t know the final mortality rate until everyone’s either dead or recovered. While anyone has it, it’s preliminary, and it’s called the CFR. Happy to dig the report up for you but this is just a logical conclusion.
CFR matches IFR not when all cases are diagnosed but when all cases are resolved.
As I pointed out in my earlier comment, IFR is not mortality rate. It is the fatality rate to date of those who have been infected. IFR equals mortality rate at the end of an epidemic. CFR will only equal the mortality rate at the end of an epidemic if all infections have been diagnosed. That is, if C=I.