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Predictions:
#1.
So at the end of season 3, Admiral Konstantine was killed. Since he was part of Thrawn's group of commanders, who will take his place? Well, who was Thrawn's right-hand man in the EU? Admiral Pellaeon. Heck, we got Thrawn back. Why not Pellaeon?
#2.
We've seen how the A-Wing was the original standard-issue Starfighter of the early Rebellion. We've seen the first prototype of the B-Wing. We've seen how the Rebels got their hands on the Y-Wing and started producing their own. So that just leaves the iconic X-Wing. Will we be seeing how the Rebels got their hands on the galaxy's greatest Starfighter? Could the X-Wing have been reverse-engineered from a TIE-Defender?
#3.
The return of the Gungans. Since Naboo is logically under Imperial oppression, it only makes sense for the Gungans to have their chance at being part of the Rebellion.
#4.
The backstory of Mon Calamari. The Mon Calamari are a prominent part of the Rebellion, so it makes sense to get a bit more backstory.
Desires:
#1.
Tyber Zann and Urai Fen returning to canon. Those of you who have played Star Wars: Forces of Corruption know who I'm referring to.
#2.
Ships colliding at hyperspace speeds. Random, but simple. It would look epic.