Yes I completely agree, timing of a recovery will be imperative but that is more a question of when, not if. The alternative in itself is not sustainable. We are either all driving a lot more, which is unsustainable. We could be working from home in greater numbers, which is sustainable to an extent (i.e. 100% wfh is unsustainable and it would damage the entertainment and hospitality industries, yet 0% wfh is unsustainable too).
WFH may actually mean more rail use, as an example someone driving 10,000 miles and then works 100% from home (unlikely I know but other options could also create more rail use too):
Travel between home and work 6,000 (no longer done)
Local travel of up to 3 miles 2,500 (mostly done by walking/cycling)
Other longer distance travel 1,500 (mostly done by public transport)
As such although overall travel has fallen the account by public transport has increased significantly.
Over the whole country a 2.5% switch from road to rail would offset a 20% fall in rail use.
Given that not all jobs could be done from home, that many jobs would still have days in the office even where there is working from home, that as a nation 25% of rail travel isn't associated with commuting or business travel, that with the fall of Flybe flying isn't going to be so attractive, and so on. As such a 20% would be quite a high percentage fall.
However that would likely be across road and rail. Given that cars are expensive (average is over £3,000/year with few, other than those don't very low milage, being able to run a car for less than £1,000/year) with a lot of upfront costs, a significant fall in travel is likely to impact car use significantly (as indicated above).
As such a lot of people could be better off by getting rid of their cars (especially if that's reducing the overall number in a household, typically from 2 to 1, rather than not having a car at all) and walking/cycling & using public transport for what's left of their travel.
1,500 miles is an average of 125 miles/month, for a lot of people that probably fairly typical for a years worth of holidays, visiting family, day trips, attending events, travel associated with hobbies, etc.
If you are doing 4,500 miles a year by car and it costs you £2,000 then that's 45p/mile. Whilst rail is expensive is rarely that much on a per mile basis.
For the family holiday then chances are the cost of hiring a car starts to be a sensible option at those milage costs (or at least isn't that much more).
Anyway, to being this all back on topic, chances are the growth of rail passengers beyond this year, maybe a bit more, is likely to continue and so extra rolling stock is likely to be required.