The series isnt about vader but whole new characters.
"First up, the Stars Wars TV series that weíve been hearing about since Sith came out. ďThatís not going to happen probably for another year and a half while we develop scripts and everything else. But itís fantastic; weíve got some incredible writers. Itís going to be much darker, much more character-based, and I think itís going to be everything the fans always wanted the prequels to be. Theyíll be one-hour episode. It takes place between Episodes III and IV. Itís going to be all-new characters, maybe a few bounty hunters in there to start the series off." - Rick McCallum