The IATA slot rules regarding 'use it or lose it' have been suspended for the full Summer 2020 season so there is no requirement for airlines to use the slots they hold until the Winter season commences.
In the UK, it is not a requirement that the airline that holds the slot operates it. Slot leases could be signed by any LGW operator to provide slots to another carrier thus ensuring they keep hold of the asset in the long term, but comply with any utilisation rules in the short-term.
The question is.....will there be more LGW slots available to would be operators than there are operators that want to use them?