People poking around the Star Wars: Battlefront beta files on PC have found mention of other iconic heroes as well as something called Hero Hunt or Hero Battle.
The files mention the Emperor, Han Solo, Princess Leia and Boba Fett. Mined sound files attached to these characters can be listened to on SoundCloud. Thanks AGB and Reddit users TheeUberMedic and radgamerdan.
The sound recordings are curious. The Emperor's specifically reference killing Princess Leia, Han Solo and encountering Luke Skywalker. Whereas Leia references killing the Emperor and encountering Darth Vader. Han Solo, on the other hand, references killing Boba Fett and encountering Darth Vader. Could this be some kind of multi-hero battle? This thinking is fuelled further by the words "herobattle" and "herohunt" in file names.
In the currently open Battlefront beta (on all three platforms - PC, PS4, Xbox One), only Heroes Luke Skywalker and Darth Vader are available. We do know, however, that the Millennium Falcon - and presumably Han and Chewie piloting it - will be a Hero power-up during the 20-player Fighter Squadron mode, which isn't available in the beta.
Incidentally, the actors voicing the roles aren't the original Star Wars cast, although they do fairly close impressions. I imagine if EA had secured major film talent it would have shouted about it, and it hasn't.