The fourth and fifth generation iPad have the exact same chassis design. The only exterior differences are the choices of color and the word "Air" next to the word "iPad" on the back of the fifth generation models. Past that, they are externally the same and cross-compatible with each other's cases. No flash on either. Mics, and sensors are all in the same place. Otherwise, A14 Bionic with 4GB of RAM on the fourth generation model; M1 with 8GB of RAM on the fifth generation model; Center-Stage on the front-facing camera. Not many hardware differences (if any) beyond that. Decent chance that the iPad Air won't suddenly add a flash until they're ready to introduce a new or even tweaked body style considering that they just introduced the current body style two years ago (and iPad body styles REALLY seem to last for a long time).