Its not simply a supply and demand question.
In general people with big houses are now older. But they are also generally more financially secure. So home loses due to job losses / not being eligible for furloughing are less likely as owners will have smaller mortages so may be more able to remortage. Deaths in older groups are higher so there will potentially be more houses from this - though many deaths are for people already in residential areas (remembering home ownership in older age groups is much higher too).
But there is a big cavet here.
a) I don't think we have had enough deaths to make a huge difference in the number of homes becoming free due to coronavirus deaths when you spread them across the country.
b) You are getting many more (younger) people in the lower / middle steps of the housing market who are more vulnerable to job losses / home losses due to high mortages relative to income (bigger mortage multiplers).
What you will see is the lowest rung of the ladder having relatively sustained demand, so any price drop here will be minimual. Its likely to be more like a slight drop but a prolonged stagnation in price.
The next step is more difficult. This is small 3 bed family properties and this is where I can see problems emerging. Its already a problem with people unable to move up the ladder from this step and many are struggling to move up from this step. You might get some repossesions but its a younger ownership, so there is room for payment restructing rather than repossession / remortgaging (its financially risky for banks to push too hard under these circumstances otherwise the whole market might collaspe so its more in their interest to restructure payments rather than lose money themselves through a wave of repossession).
Those who feel they want to move up the ladder because of more availability of property will struggle to sell though. There may be more demand to, and there may be more opportunity to with larger houses to move to.
c) So your basic problem is that there will be very little movement in the market. There may be lots of bigger properties available but there simply won't be fluidity of movement because not enough people will be in a position to actually move because chains are incomplete.
There might be a lot of people who want a quick sale, but you are still going to need to be in a position where you've sold yourself. And that means people moving up the ladder from lower down. That can't come from wage growth (not happening for some time now) and windfall from inhertience will be limited and not as large as it might of been (precisely because of the lack of liquidity of the market and inability of people to move up). Banks are going to be very wary of risky lending atm, so unless you have a super secure job you may struggle to get a new mortgage or government stepping in to provide lenders with reassurance (more likely).
d) There is less likely to be people moving because 'they want to'. Which could result in less properties being available full stop. People don't want to take the risk to move right now / have the ability to move right now.
The basic problem is the 'vicious circle' problem where the whole market is locked and stagnated through a lack of ability / willingness to take a risk to move.
For things to become more fluid, you need an injection of cash (through wage growth) or a big crash in the market with lots of people with cash in hand and a general lack of demand. We still have high demand for housing at lower levels, so a crash isn't likely - there will be enough demand and a small dip in prices. Your middle tier of the market is the one thats been causing problems for the last 5 years now which hasn't been widely recognised and Covid-19 is only going to make that worse.
So yeah. Middle market stagnation is your problem. Estate Agents are going to go out of business as a result.