These stamps were announced by the USPS on March 6th:
For one week in May 2026, the world capital of stamp collecting will be Boston, host of the Boston 2026 World Expo, the 12th international philatelic exhibition of the United States. To build anticipation and commemorate this confluence of art, history and international goodwill, two intaglio-printed stamps will highlight the special role of Boston in the American Revolution as we prepare to celebrate the nation’s 250th anniversary. Greg Breeding, an art director for USPS, designed these stamps with digital illustrations by Dan Gretta featuring the Old 
North Church and a “midnight rider” on horseback in Colonial garb.
No date of issuance or city was given. However, many philatelists expect them to be issued at Great American Stamp Show in August. The latest information will appear below the line, with the most recent at the top.
It’s interesting that the USPS says the second stamp shows ‘a “midnight rider” on horseback in Colonial garb’ rather than Paul Revere, William Dawes or anyone else.