Two big things (for our purposes, at least) came out of Celebration’s Rebels panel. It will be the show’s final season, but Grand Admiral Thrawn’s bodyguard (in the books) Rukh will make an appearance before it’s gone for good. The character will be only the second character from the Thrawn trilogy to make it to canon on Rebels. And, the kicker: He’s being voiced by Warwick Davis.
Given the timeline, I wouldn’t expect him to play quite the same role in the show that he did in the books – but you never know.
The show itself ending is not a particularly big surprise, but as Dave Filoni pointed out at the panel, this gives him a chance to take it out properly. This certainly won’t be the last we see from Lucasfilm Anaimation – and I’m not talking about Forces of Destiny.
We also got to see the first episode of S4. I won’t say much, but it was the first part of a two-parter set on Mandalore.