I suppose it's all down to politics and the structure of the railways, not to mention the chancellor's purse strings, to even begin to guess the era post 2026.
Its all down to politics. The other things follow from that.
If the right wing of the Tory Party seize that party and take power, then we are back to managed or unmanaged decline as roads are built to provide capacity for the private car and the Lorry, that suit their ideological world view.
If the left take power then we are probably looking at something like we have at the moment with publically owned
TOCs▸ .
If we oscillate between the two its anybody's guess.