The first guests have been announced on the BotCon website, but only as people in the Dealer Room for attendees to visit and seek artwork and/or autographs.

Artists include - Marcelo Matere, Dan Khanna, Josh Perez, Robby Musso, Casey Coller. Some of the IDW people may be on the IDW presentation panel as well. (at least it is a better turnout than last year of only 3 IDW people)

I'm not a fan of the current BotCon owners announcing guests after pre-registration is open (and usually sold out), as it shows they are more interested in selling toys than getting people to actually come to the show for its features. It's kinda, what's the point now? They have the attendees guaranteed now, to come and collect their toys... why bother trying to make the show anything special now (which some years recently is how the convention ends up turning out for attendees who aren't too fussed about the exclusive toys).
But for those who aren't able or want to go to BotCon, the toys are probably the main interest, as it gives those who can't make it, a chance to have something BotCon-ish.