It may not be a trailer for Episode VII, but Twitch.tv recently showed viewers an hour of pre-alpha footage of Star Wars Battlefront III, thanks to Past to Present Online. The footage is glitchy and rough, but it gives a good idea of what might've been.
While you're at it, you may want to pour one out for the also cancelled, BobaFett-themed, Star Wars 1313.
[via Twitch.tv]