So looks like Thrawn's back where he belongs:

http://io9.gizmodo.com/thrawn-isnt-the-only-surprise-in-the-star-wars-rebels-s-1783780241

Holy crap. Rebels has a new Big Bad, and it’s an old Big Bad—Grand Admiral Thrawn, the brilliant Imperial military commander who took over the remnants of the Empire in the old Expanded Universe, as revealed in the very first EU novel trilogy by Timothy Zahn.Some things to note: 1) He’s definitely referred to as “Grand Admiral.” 2) There’s no mention of anything else from Heir to the Empire or the other two books of the trilogy, so don’t go think those novels have suddenly been added wholesale to the new canon. 3) He’s being voiced by Lars Mikkelsen, brother of Rogue One star Mads. 3) Timothy Zahn sent a video message giving his full approval. Nice!

Aaand, seems Zahn will be revisiting the Grand Admiral in a new book, out sometime in 2017.

Update: Zahn is writing a new Star Wars novel titled—wait for it—Thrawn, due 2017. This isn’t just a cameo, guys.

Not too shabby!

I was seriously about to make this topic. Guys should be all over this like flies on ****, this is ******* amazing. Finally, someone competent is writing for Star Wars again, and one of the most important anti-hero antagonists is back.

I hope he doesn't die or become completely irrelevant or shoehorned into Chuck's awful Aftermath series.

http://www.ign.com/articles/2016/07/16/star-wars-celebration-2016-grand-admiral-thrawn-is-now-canon