Young Impa is playable in The Legend of Zelda: Breath of the Wild prequel Hyrule Warriors: Age of Calamity.
Developer Koei Tecmo showed off Young Impa gameplay during a Tokyo Game Show 2020 broadcast. (Skip to 1:35:41 in the video below to see her in action.)
Hyrule Warriors: Age of Calamity tells the story of the battle against Calamity Ganon, which occurred 100 years before Breath of the Wild. In Breath of the Wild, Impa is the elder of Kakariko Village, the village of the Sheikah people. She guides Link and talks about some of the events of the Great Calamity, which we will now get to see in Hyrule Warriors: Age of Calamity.
As you'd expect, Impa looks much younger than she does in Nintendo's open world masterpiece. We get a decent look at her ninjutsu moves and her ability to create blue clones of herself during combat.
The broadcast is well worth a watch to get a sense of what Hyrule Warriors: Age of Calamity actually is. My initial impression: a narrative-driven Musou game.
Young Impa for Smash, then?