I would not be surprised if Red Dead Redemption II opened with the Blackwater Massacre as the description given by Rockstar for Trailer 3 states, "After a robbery goes badly wrong in the western town of Blackwater, Arthur Morgan and the Van der Linde gang are forced to flee. With federal agents and the best bounty hunters in the nation massing on their heels, the gang must rob, steal and fight their way across the rugged heartland of America in order to survive."
Whether we'll see Heidi McCourt is still up for debate as that would mean the game's story would have to span from 1899 to 1906 when John Marston got shot and left for dead, if the game's story does indeed take place over several years I think it would be amazing and unless I'm mistaken it would be a first for Rockstar.
The blonde man in the trailers is Micah Bell, one of Dutch's favoured gunmen. His name as well as the names of many other unnamed characters from the trailers was revealed to various journalists when Rockstar gave previews of the game.