I think it's been going since the first week of January 2020, so for two years and two months.
You have to wonder how many people have paid almost double the price for a single from London to Wakefield for example during that time.
It seems unlikely to me that a full rollout will take place, even if only period returns are cut in half. A single from London to Barnsley on route Chesterfield would drop to £42 for example. Is that really going to happen? Haywain made his own personal opposition to the London to Edinburgh rate being capped at the current Super Off Peak times very well known for example, and I imagine that's precisely the view in many commercial departments i.e. that there should be more flexibility to charge higher rates within the current Super Off Peak times because some of the trains running at those times can easily be filled at higher prices. At least with the current system of returns the customer has to pay the Super Off Peak rate both ways if they want to avail of it.