It was also announced on the BotCon website along with their Tarantulas toy reveal, the Voice Actor for Tarantulas (Alec Willows) is their second guest next year. (along with David Kaye)
This will be Alec's second BotCon, with his first appearance being 16 years ago in 2000 (ironically, it was the same year that had John Moschitta's only appearance before returning this year after 15 years). He looked like he was about 70 years old 15 years ago, so I wouldn't be surprised if this was his last BotCon appearance.
That's two Predacons accounted for, and almost all Transformers cartoons since Beast Wars (with David Kaye voicing Transformers roles in every series after Beast Wars except RID-2001). While on the other end of the spectrum, Alec Willows has only ever voiced one Transformers cartoon character - Tarantulas.
Speaking of David Kay, next year will be his ninth BotCon (ten if you count 2003), which will make him the most frequent BotCon guest, just jumping ahead of Peter Cullen who is still on eight.
I imagine that Richard Newman (Rhinox) would also be a guest next year, as he went through some financial troubles a year or two ago, and has been invited to a number of conventions since.
It would also be good to cross off the remaining Beast Wars voice actors who haven't been a BotCon guest yet...
Don Brown - Scorponok
Colin Murdock - Quickstrike
Lee Tockar - Ravage
Carol Slavenkoff - Predacon Computer
Unfortunately, Cambell Lane (Rampage) died before being a guest.