It would be a pretty annoying disappointment to have spent this much time with Cad Bane during the course of the series' run and get no closure to his story. I wouldn't mind if he just sees the writing on the wall, disappears into the background of the galaxy and is never heard from again, but I'd certainly like to know what happens to the guy. Something. Anything.
He's been one of the most important of all the secondary characters and I think he deserves a little better than "oh, well. The series is over. Use your imaginations or wait for some future book or graphic novel."