Fortunately the monkeypoxvirus mutates 100 times slower than SARS-CoV-2. 10 times slower if you count the APOBEC3-induced mutations.
Thing is... it'll be under tremendous evolutionary pressure during the next few years to get rid of the latter, and that's an enzyme with antiviral properties. It might even be one of the reasons MPX actually has just a 0.01% case fatality rate.