We know for sure that the two big lucrative sources of industry revenue aren't coming back in the short term: long-distance daily commuting from the East and South East of England into London, much of it on very costly longer than monthly season tickets, and high yield business travel, much of it corporately funded and much of it First Class.
Set against this, the provision of passenger railway services is simply far too expensive, especially on routes where trains are short or diesel powered (or, of course, both). Obviously there are lots of different long-term reasons why, but we don't really have a long term plan or a long term governance process. The immediate concern is that their real cost is reduced. If it cannot be reduced, it's then a question over which services we can do without. That's the fundamental question here. Unfortunately I think many people still haven't quite accepted that, although I do sympathise because it's difficult to imagine that after so many years it's going to change.