Welcome to the forum Gunboat4.
Airline schedules, as you'll see from this forum and others, are more fluid than they have ever been - so airport changes for flights are also more fluid.
So, for BA, the LGW-MCO route is not showing actively accepting bookings until 7th June 2021 but of course this can slip depending on UK and US travel restrictions. Whereas BA is actively accepting bookings LHR-MCO from 17th May 2021, presumably linked to UK travel restrictions and as with LGW-MCO this can also slip depending on UK and US travel restrictions. BA, when operating on a dramatically reduced schedule as at present, could move all flights for booking purposes at least to LHR but operationally once things open up to any real extent they simply don't have enough take off/ landing slots at LHR to actually fly a majority of the routes without dropping some other routes.
For VS it is in a different situation to BA in that with route additions and deletions previously announced it could operate the vast majority of it's routes, with some frequency adjustments, using LHR slots it has access to. This doesn't mean VS will never return to LGW - if demand on business routes grows back then it will want to use it's LHR slots for that market and would look to move leisure flights back to LGW. My hunch would be that we might see VS operating some, but probably not all, leisure flights again from LGW in late 2021 / early 2022 but there are probably much better hunches among other forum members on which routes would be likely to move first if/when that happens (as that then moves into the realms of aircraft types and configurations as you don't want to run excessive 'positioning' flights moving empty aircraft between LHR and LGW several times a week to meet schedules).
For both BA and VS the slots issues at LHR and LGW and therefore their scheduling will be affected by when the moratorium on 'use it, lose it or sell it' expires as aviation reopens.....at some point the normal procedures worldwide for slot-limited airports will mean that airlines will again have to either use the slots they have or sell them to another airline or they simply lose them.
In summary, the short answer is that my hunch is BA is far more likely than VS to be operating LGW-MCO in the immediate future but both could be by February 2022!