"That in itself shows people regard the interaction they had with the company as a purchase, not just temporary access that can be removed unilaterally on a whim."

and of course an end user believes it's a purchase when the companies explicitly say things like "Rent for £2.99 or Buy for £9.99".

If Sony want to market this as buying rather than renting a film, then I think that they need to either -

- negotiate a contract that "grandfathers in" availability for as long as the platform exists, even if they lose rights to sell to new customers - refund what it'd now cost to buy outright elsewhere if they're pulling the title (if they want, maybe pro rate that. e.g. count a purchase as 100 years of access to it. If I lose rights after 10 years, I get a 90% refund)