Sam Wilson's Captain America shield almost got upgraded in The Falcon and the Winter Soldier. The Star-Spangled Avenger's shield is one of the most iconic Marvel weapons. So, when it was passed from Steve Rogers to Sam in Avengers: Endgame, the changes in its design were easily recognizable.
The origin of the said shield remains somewhat of mystery in the MCU, one of the questions left unanswered by Avengers: Endgame. During Steve's one-on-one fight with Thanos, the villain repeatedly hacked away at it with his sword, resulting in the shield breaking into pieces. It was never shown to be fixed, and the Avenger didn't bring it with him when he left to return the Infinity Stones at the end of the film, but Old Steve still returned with a new version to pass off to Sam Wilson. Despite the lingering mystery, the redesigned Captain America shield was prominently featured in The Falcon and the Winter Soldier, first wielded by John Walker, and then eventually Sam, as he rightfully assumed his place as the MCU's new Captain America.
In Marvel’s The Falcon and the Winter Soldier: The Art of the Series (via The Direct), new information about the defensive weapon is released. The concept art from artist Wesley Burt reveals that Captain America's shield almost got new upgrades in The Falcon and the Winter Soldier, including the ability to conjure an "Emergency Energy Shield," which "spreads from the rim of shield for quick group protection." This feature is inspired by Wakandan tech used by the Border Tribe in Avengers: Infinity War. Among other scrapped special features for the shield include the ability to offer an expanded protective barrier and the ability to be attached to Wilson's wings. Burt talks about the process of developing these upgrades in the quote below:
Ryan [Meinerding] asked some of the [Visual Development] department to take a little bit of time and think up some new ways that Sam could use the shield, more specific to him and his own physicality with it… when I was thinking about the tech rim piece, I was looking for a way to minimally add an element to the shield so as not to distract too much from the shield itself but still make it feel like it could have a believable tech addition and hint at the Wakandan upgrades before you see them used.
I also just really wanted to think of other ways that could emphasize the defensive nature of the shield itself and not just look for new ways that it could be used as a weapon. I immediately thought of the various shield tech used by the Border Tribe and their blue cape shields, and also the big cloaking shield around Wakanda itself, as a jumping-off point for how it could be implemented here…
The upgrades mentioned in the behind-the-scenes book seem to be pulling a lot from Wakandan technology. This makes sense, considering that Bucky asked the help of his Wakandan friends to make Sam the Captain America suit that he debuted at the end of The Falcon and the Winter Soldier. Considering the fact that the shield itself is made out of Vibranium, it isn't outside the realm of possibility that during Steve's final time travel mission, he made a pit stop in Wakanda to request the redesigned shield that he ultimately handed out to Sam at the end of Avengers: Endgame.
In any case, just because these upgrades didn't debut in The Falcon and the Winter Soldier, it doesn't mean that they're permanently scrapped. If anything, perhaps they are being saved for Captain America 4, which will continue Sam's story as the MCU's new Captain America. The design of the shield itself hints that it has some secret capabilities that Steve's version didn't have. It would be exciting to see Sam fully utilize it when he returns to the big screen through his own film.
Source: Marvel’s The Falcon and the Winter Soldier: The Art of the Series (via The Direct)
