The uniform Russell wears appears to resemble a combination of the classic Cap suit (shield included) with details from the U.S. Agent uniform, which bears the question, is this man going to be the new Captain America?
If so, that would explain why Sam Wilson is still using his original Avenger alias, but how Walker got ahold of that vibranium shield (if it is the true shield) is another question.
The answer may not be found in the Disney+ Super Bowl ad, which even shows Sam Wilson tossing the shield around, clearly practicing to be the new Cap, but in recently uncovered set photos that reveal series star Wyatt Russell as John Walker, a wounded war veteran who has taken on many aliases in the comics, including that of Captain America, but most recently U.S. Agent.