I'm biased, but I hope Dorian is a companion but not Cole, and thus I'm grasping at every straw to convince myself that will happen.
Cole is a child, and I don't want a child in my party, this is serious business for grown-ups, and beyond that I don't see what Cole would bring on the table. Dorian meanwhile would have the always interesting point of view of a former "insider" who became sick of his homeland's antics, but still wants to improve it.
I don't have any problem with having a child in my party. It'd be sort of like Grunt all over again, except Cole is both more dangerous and more personable. And, he might be a bit more mature than he was in Asunder. I'm not thinking "fully adult mind," but more along the lines of "sort of like a teenager." Everything was scary to him in the book.
But, I'm of the opinion that, since we've seen virtually no art or screenshots or videos of him--unless that's him in the screenshot of the party vs. the troll--he's probably not a companion. And personally I think that's a shame, because I do want Cole to be one of the final two companions, mostly because he's bound to have some unique perspective on the spirit/demon dichotomy, and spirits and demons in general. Assuming, of course, he can parse any questions you happened to ask him.
As for Cole's combat ability, well... time has passed since the novel and Inquisition's setting. Not only that, but everyone starts at level one. And, he did help fight the archdemon in the Fade. Give the kid a fair chance.
That said, I believe our final two will be rounded out by Dorian and either someone we don't know about yet, or Cullen. I'd rather we have one more female and Cole, but I don't get to make these decisions.