Originally Posted by
thefiverivers
....If you cancel, you won’t be able to use your Card Account for new transactions and you’ll forfeit any rewards. In addition, cancelling your Card will result in a prorated credit for any Annual Membership Fee paid in the last year."...
I read this to mean that declining the replacement card immediately closes your Mercedes Benz Platinum account, and your Membership Rewards balance may, or may not, also expire depending on the other American Express cards that you hold.
Read here, in particular the
Forfeiting Points tab:
https://rewards.americanexpress.com/...v=footer-tandc