Here's how I think the finale of TFATWS is going to go.
We have two people claiming the Captain America title, with one common goal: stop the Flagsmashers.
The main ideological battle of the show is what kind of Captain America do we want and can accept as the symbol of our nation. I think the final episode will cement itself in favour of Sam by juxtaposing him directly against John Walker, in moment when they're trying to achieve the same goal. They both have different reasons for stopping the flagsmashers and therefore different strategies.
John Walker is avenging something personaI. There's a lot of rage there. His background is already cemented in war crimes (in Afghanistan presumably). He is the American government.
Sam Wilson is a pacifist, and his background is in helping veterans with PTSD since his own wingman died. He's been anti-government ever since we met him, and has stayed that way.
Sam Wilson's race and his anti-government history means he's going to be a divisive Captain America. I don't think the US government is just going to roll over and accept him the second he shows up. I don't think that would be true to what the show has been about so far. The conversation with Isaiah will not be discarded as a cynical old man's drivel, and Sam Wilson's Captain America, though a better choice to anyone with a sound mind, will have to stay on the run.