A fair few guests have been announced - https://www.starwarscelebration.com/Guests (though not sure how up to date that is).
I hadn’t realised the delectable Katee Sackhoff had been in Rebels & Clone Wars!
I had read somewhere - and can’t remember where - that Oscar Isaac may be appearing too.
Aye, I think that’s Chewie - who’s about to pull the arms off JJ 😉