So that confirms a few things:
Looks like we'll see the Rogue One crossover episode, though not sure if that'll be season finale or if they'll focus on battle for Lothal in the finale. Guess we'll have to wait and see.
Also, Season 4 will reintroduce Rukh, Thrawn's Noghri bodyguard from old EU, voiced by Warwick Davis. Awesome.
But seriously, what are odds any of them make it out of the season alive? I can see a few surviving, like Hera, Chopper, maybe Sabine, but Ezra and Kanan are unlikely to live through finale due to, you know, continuity... unless they explain what they were up to throughout Original Trilogy era in new continuity... which is completely possible with new canon once Season 4 is over with early next year, through novels or comics.