Page Six has the first set photos of Wyatt Russell, that's Kurt Russell and Goldie Hawn's son, in costume on the set of Marvel's The Falcon and the Winter Soldier series.
Russell is playing John Walker. In the comics, Walker was an extreme vigilante called Super-Patriot, who took over as a more violent Captain America when Steve Rogers walked away over a disagreement about government oversight. When Rogers returned to the role, John Walker became U.S. Agent, the government's officially sanctioned shield-slinging operative.
But back to the MCU, you may remember that a retired Steve Rogers handed off the shield to The Falcon at the end of Avengers: Endgame. This seemed to set up Anthony Mackie's Sam Wilson taking over as the new Captain America. The set photos suggest that Walker may actually be stepping into that role, or attempting to at least. The TV series is set to follow the adventures of Sam Wilson (Anthony Mackie) and Bucky Barnes (Sebastian Stan) in the post-Endgame Marvel Universe, so it looks like we'll find out what the deal is when The Falcon and the Winter Soldier debuts later this year on Disney+.