I'd feel safe betting that the Native American on the cover(like the same one in the trailer) is playable, and probably the female. Though I'm curious why she's not on the cover, unless that's a deliberate misdirection.
To wrap everything back together for everyone. A few months ago many voice actor profiles were found and linked to the VO's of the first game, who are back to reprise their roles. Three were found of particular interest, I'm pretty sure now, after the trailer, that we've found our three protags.
Three Protagonists.
Roger Smith is playing Arthur Morgan.
Noshir Dalal is rumored to play a currently unamed Native American, who was likely seen in the trailer, he was also in
Fallout 4 for a voice comparison(funny enough the PC in the video is named Dutch lol). It sounds like him(no doubt), and looks like him to a degree, imo.
Cali Moore is playing an unnamed female, who is very likely the blond in the trailer. Looks like her(that nose dip), but she's a pretty unknown actress so sound comparison is difficult. With the particular interest put on her in the trailer, it seems likely that she's a protag too.
http://www.neogaf.com/forum/showthread.php?t=1352263&highlight=red+dead