第9世代について、比較的信頼性のあるmark gurman氏の寄稿によると新ipad proと共に計画中となってるね。
発売時期までは触れてないけど。

https://www.bloomberg.com/amp/news/articles/2021-01-15/apple-considers-foldable-iphone-minor-changes-planned-for-2021-models?

For its tablet line, Apple is planning a new iPad Pro that looks similar to the current model but adds a MiniLED display and much faster processor. A thinner and lighter entry-level iPad that uses the same design as the 2019 iPad Air is also in the works.