All right, do note however that "linking" is not the same as "transferring".

Linking is what we had to do to get the Token/Satchel thingy, while transferring will move you over to the new payment method(s) and enable you to actually manage the account.
While it was supposed to become mandatory some months ago, they postponed it due to the obviously dis-satisfactory payment methods they were offering at the time.

Or at least I haven't seen an announcement of it becoming mandatory yet, so if one has the payment going OK still, it may not be. However for me example, a couple of months ago when it first was supposed to be forced, I had a payment issue (or more like they had an issue with the payment, as my account was fine, and I would have just needed to re-enter the same card number for whatever reason), and I obviously couldn't update the payment info via POL any more, so I was forced to transfer at that time.

So while everyone is not forced yet by the service, things like this in the system may do it instead.

You can at the SQUARE ENIX Account Management site in your Options or Services List if there is something along the lines "accounts that need to be transferred blah-blah".

Note for anyone not yet transferred, one will have to start using one of the new payment methods after doing so.