I'm sure you are right, TG.
Can the railway, in the medium term, adjust to these changes? The answer, if we let it, must be yes.
Should the network be allowed to permanently shrink? Emphatically, no!
I don't disagree, however "the railway" shouldn't sit back and allow it to happen - there is much they can do proactively, particularly improvements in the area of leisure travel, working practices and installing a culture of promoting customer service/experience which could help to mitigate against a future of fewer passengers.
Culture can be the hardest thing to change/adjust in any organisation, especially one which is still firmly rooted in a monopolistic public sector mindset, but in this respect, even the railways can move more quickly.
They may have to, if aforementioned "shrinkage" is to be avoided.