Mines not moved much since the 1st lockdown, as I've been working from home full time too. I've done a total of 1010 miles since getting it, so it's been a bit of a waste.
My concern is, and would be in your shoes, that if you aren't maximsing the benefit of actually having the car then the longer you hold on to it the greater the likelihood of some seismic improvement that would affect residuals
Like you I have a M3P with FSD, and I think that's probably the most exposed - e.g. if a Ludicrous/100kWh Model 3 comes along then it will no longer be the fastest available, and it isn't already the longest range, so it would sortof be in no mans land. It would be even worse if this 100kWh model replaced the existing M3P at the same or similar price point.
One could argue the 2021 changes will have had some kind of hit, and that is likely to continue with iterative improvements.
I don't think there is a "right" answer. Assuming a normal level of depreciation is probably a sane way to look at it. I don't think we'll see a £30k price cut overnight that S/X owners saw, but I could forsee HW4 or 100kWh Model 3s having a disproportionate overnight effect on residuals.
For what it's worth I got a trade in value from Tesla of £52k for my M3P, which I thought was very good, but it would still have cost me another £13k to get into the same car in 2021 spec. I didn't think the changes were worth that much to me.
