Yes, Deepika Padukone is confirmed to be in Brahmastra Part 2: Dev. She plays the role of Amrita, who is Ranbir Kapoor's (Shiva) mother in the film.
Deepika's character, Jal Astra, was first introduced in the first film, Brahmastra: Part One - Shiva, as the mother of Shiva and a powerful, enigmatic figure.
In Brahmastra Part 2: Dev, we'll see more of her story unfold and her pivotal role in the film's larger narrative.