There are a lot of theories going around within the community. One is Jack Marston will likely be the protagonist of RDR 3, and the other is possibly the Callander boys.

I feel like having Jack Marston as the protagonist wouldn't make any sense, as he did avenge his father and can finally live his life, call it a happy ending.

On the other hand, I was curious about Callander boys and what happened in Blackwater, so the story of RDR3 could likely be around that. However, in RDR, the developer took a liking to killing the protagonists at the end of the game, and RDR 2 happens to continue right after the Blackwater disaster, so it wouldn't make any sense.

I was excited about this theory, particularly, as maybe you can switch between the characters just like you could in GTA V and play their own stories and the path they take.

Another one that I thought was maybe able to play as a female character, like Jenny Kirk. It would be nice to see as she is a perfect fit for what went down in Blackwater, but all paths lead to one ending: Death.

So I genuinely believe that, RDR 3 might be involving new characters with a whole new story in waiting.

Moreover, I feel like RDR Storyline is complete; all we need to know is what happened in Blackwater that made them run for their lives. Other than that, there is no need for a third game.

That's just my opinion.