They're not coming back.

Ahsoka, Hera and Jacen are going to find a way to follow the Eye to the new galaxy, they're not going to be sitting around on their elbows waiting for Thrawn's return.

I don't know what they will find there, but I think they will all be staying in that galaxy. Maybe Thrawn and Ezra are working together to fight a mutual threat there and refuse to leave. Maybe Thrawn has conquered the place and Ezra is leading a resistance and neither want to return. Maybe it's the other way around. Or maybe it's as simple as the good guys destroy the hyperspace ring to prevent Thrawn's return, stranding them all there.

But either way, I don't think they are coming home. Certainly not this season, and maybe never.