Evidence has surfaced that Darth Vader will be in Rogue One, the first “anthology” Star Wars film. Devin Faraci of Birth. Death. Movies. has it from a “good source” that Vader will appear – onscreen – in Star Wars: Rogue One. It isn’t expected to be a large role, he may appear via viewscreen or hologram, and is likely not the primary antagonist of the film. (Though it’ll be implied he’s the one pulling the strings behind the scenes, and of course we know who’s pulling his strings, and anyway…)
Obviously, it’s too early to know whether Lucasfilm will seek out James Earl Jones to reprise that iconic voice, as he did recently for Star Wars Rebels.
Source: Birth Movie Death