My annual fee of $650 posted on 12/15 and I was on the fence if it's worth it for me to keep it. Last year I still paid the lower AF so still found it worthwhile. I did pay the AF when it was due, but today I decided that I'm going to downgrade it to the legacy Bonvoy card for a pro-rated refund of the AF as the benefits are not compelling enough for me to keep it.
In the disclosures for the downgrade which I did via chat, the rep stated the following which confirms that I (and anyone else who downgrades post renewal) will still receive the 85k free night:
The redemption level for the Free Night Award benefit you receive is based on the Card product you have at the time of your renewal. If you transfer to a different Marriott Bonvoy American Express Card, you will still receive the Free Night Award benefit for the Card product you had as of your renewal date.