Nothing has been announced, but if past practice holds, a new  large-format stamp featuring a National Park or natural wonder will be issued for this rate on Sunday, January 24, 2021, the date the rate goes into effect. There will not be a first day ceremony and in-person cancellations will be hard to obtain.

Updated December 26th:

Since the Express Mail flat rate charge is not changing, Linn’s Stamp News does not expect a new stamp to be issued. This listing has been removed from the VSC’s 2021 U.S. Stamp Program.