my thinking is the end game will be zelda taking on ganonImpa now basically counts as the Sheikah Champion as I always envisioned her. I even think she's just about the most likely and obvious first party newcomers right now! I haven't seen her fight yet in Hyrule Warriors 2, but we sort of know what to expect already right?
In a way, I think Impa will low-key be one of the main characters in Hyrule Warriors 2. Why? All the Champions will die, that's canon. Link will too, but be brought to the Shrine of Resurrection, Zelda will use the light magic to lock herself and Ganon in Hyrule Castle.
So who remains ???
That's right, IMPA! We literally see the part in the trailer where Link falls! I can't see that being the end of the game honestly. I think there will be an end game where Impa takes over the leadership role, and escort Link's unconscious body towards the Great Plateau. Probably even fight the final boss of Hyrule Warriors 2!
So this means , that Impa was yet again a key character behind the scenes of Breath of the Wild! This is truly reminiscent of what she did in Skyward Sword, but in reverse! We meet old Impa first, and then discover young Impa and what she did way later!
If nothing else, I could see her end up being a Echo to Ryu Habusa, which would make sense if there's to be a Echo Fighter outside of the franchise for Impa.
I'm confident Impa will make it now. :D