They also lost a class action lawsuit over OtherOS, needing to pay people that used it $55.
With PS2 emulation, I suspect far more people do use it and it would be much, much easier to prove you used it. This could lead to a huge settlement against them.
OtherOS came with the system in the box, and Sony tore it out after consumers had already purchased the system.
A subscription service, they can just end it and refund people's money and call it a day. It's absolutely not set in stone.
Unless they decide the revenue from the highest tier is worth leaving it in place. To be determined.