We know that as of the Rebels finale/ANH, an all-out war between the Chiss and Grysk in the Unknown Regions was imminent... And I still think that Thrawn's underlying plan was to leave the Empire(without treasonously defecting) in order to help his people fight the Grysk, and likely recruited Ezra to his cause after explaining the situation to him(ie. if the Grysk weren't stopped, they would enslave the entire galaxy.) So I wouldn't be surprised if that's what Thrawn and Ezra have been up to in the ~9-10 years between the Rebels finale and The Mandalorian S02 finale.
So yeah, I think it would be awesome to see how the Grysk war plays out... Be it in live action, or a novel. Either way, Thrawn likely wouldn't be playing the villain role at all, so in that respect it would likely deviate from Heir quite a bit.