This is a major announcement that will affect all property owners in Ontario. The Municipal Property Assessment Corporation (MPAC) will postpone the 2020 Assessment Update. The Ontario Government has declared that property assessments for the 2021 property tax year will continue to be based on the fully phased-in January 1, 2016 assessed values. Your property assessment for 2021 will be the same as the 2020 tax year, unless there have been substantial changes to your property.
Toronto Storeys has an excellent article detailing the change and the reasons behind it.