It may get reconsidered in a few years when COVID is well and truly over. Then 10 years to legislate and plan and 6 years to build. 2040 if ever.
That's the story is timeframe that I was considering. I suspect that rail use could well recover well.
The reason for that thought is that at least on one half of Crossrail 2 (i.e. those passengers approaching from the Waterloo side) rail use was fairly high all day and not just in the peaks. As such whilst we could see significant falls in office related travel, chances are that's going to just result in the need for a slight easing in the need for so many high peak services.
Anyway some of those services has very high levels of use, to the point where they could see a 50% fall in passenger numbers and still have >65% of seats occupied.
It's also arguable that SWR was running too many services anyway and that a small decrease in that would give us a more reliable service.
Also it's worth highlighting that a change to WFH may actually increase rail use, in that 80% if miles traveled is by car and 10% by rail. Therefore if people are traveling less frequently then car ownership (with high upfront costs, especially for the young) becomes less financially viable and so rail becomes one of the options people would consider using more.
Based on 2019 usage a 1.25% shift from road to rail would add back 10% of the 2019 rail use. Given that if 70% of rail use being work related and 60% of jobs are suitable to be done from home and if people WFH an average of 50% of the time then that's a 21% fall in rail use (mostly focused in the peaks) and that's comparable to rail use in 2012 (when we were still talking about needing Crossrail 2), then there's still a fair chance that it could happen in that timeframe or not much slower.
Especially given we need to decarbonise our travel and rail is a good way to do that.
One final point, when I was using SWR to travel there was a lot of local travel (up to a few stations of travel) which was undertaken (I was going no further in than Woking), to the extent that at Farnborough Main there was about as many getting off as were getting on to head towards London (due in part to a lot of education related travel, but a lot of local-ish work travel) which ment that the train was full and standing between Fleet and Farnborough and would have been (at a guess) about 1/3 full at that point (bearing in mind these are 12 coach trains) even without London passengers.
Whilst there's some significant savings (time and money) for those traveling 30 minutes or more for those only traveling 20 minutes or less the savings are going to be less. As such those passengers are going to be less willing to work at home where that increases their heating costs during the winter, where there's likely to be others around (especially children) or they have few social interactions outside of work. As such it's likely that such local travel could be more resilient than the longer distance travel into Central London.
Whatever the outcome we shouldn't rule out projects like Crossrail 2, Southern Approach to Heathrow, etc. until at least 2025 when we have some idea of what post Covid-19 (or at least a note established normal has been created) passenger numbers are going to look like.