For now I believe that any official foreign travel be it outgoing or incoming is unlikely happen for the first six months of 2021. The PoW has been his mother's representative overseas for a few years now so this will impact his calendar as well as the calendars for other members of the BRF: Camilla, Cambridges, Anne, Wessexes etc..
As for July through September, we'll have to see if foreign travel will be possible ie: Anne attending the Olympics in Tokyo.
As for domestic travel and visits, I expect that those will be curtailed for a few months, though perhaps by Spring it might be possible. IMO the Court Circular will continue to list all phone and virtual visits throughout the year.