I was at the LEGO Store earlier tonight and overheard that there was, in fact, supposed to be a third Star Wars magnet set featuring C-3PO, Tantive IV Leia, and Admiral Ackbar. Supposedly, there was a printing error with Ackbar's name, and they had to make a fix before releasing them. No word on a release date.
Also, if you are at your local LEGO Store and you don't see any of the new magnet sets, ask one of the store attendants. Ours weren't out because they wanted to sell through their existing inventory. The attendant was able to get a couple from the back room for me.