Its Kylo Ren. Darth Revan is not cannon. They might be paying homage to Darth Reven, which is what they said they'd do when the invalidated all stories not connected to Lucas. Kylo Ren will be the baddie in the first film, but in my opinion he's just a pawn for a real dark lord. If you remember the story about Darth Plaugies the Wise in Episode III, I have a feeling he's going to be making his return in Episode 8 or 9. The first teaser had that voice played by Andy Serkis, I think thats the big bad over the whole trilogy. Makes sense that its Palpatines Master since it follows the original storyline.
The silver trooper is Gwendoline Christie from Game of Thrones (Brienne of Tarth). Her name in the film will be Captain Phasma.