I've called amex regarding my platinum charge renewal last month. No retention offer, but was given an option to downgrade to gold or green card. I then proceeded with the green card.
The downgrading process is fairly simple, took me a week or so to received the card plus another week for the points to transfer. No issues keeping the points, annual fee is $160 ($80 card fee + $80 enrol membership rewards).
I am quite happy with the decision as I found the platinum charge isn't worth for me right now. If your physical platinum card isn't expired the card is still linked to your green card account. Any direct debit from your old platinum card still active. From this, I have a theory that you might still be able to access the virgin lounge (as they couldn't tell if the card has been cancelled or not, besides if they swipe the card it still work!). But I doubt any centurion lounge as they could verify your account.
One surprise from downgrading is the hotel membership you've got from platinum charge. My Accorplus somehow automatically renewed which means a free night. That paid for the annual fee already. Other membership such as priority pass is no longer active.
Overall I am satisfied with green card. Reasonable annual fee and earn rate, most importantly you keep all the points.
