@Baazigar, Shuddhi isn't based on Amish Tripathi's The Immortals of Meluha, so even if Salman does it, he's not gonna be playing Lord Shiva in it. Anyways, the protagonist of TIOM, is a Tibetan immigrant as per the book, his character is highly inspired by Lord Shiva's, but he's not a god in the book and there are some characters in the book, that are taken from the mythology, but the book as well as the whole series is Amish Tripathi, the author of the novel's fictional take on the mythology.
As far as Shuddhi is concerned, it's gonna be an original film, written by Karan Malhotra and his wife, Ekta Pathak Malhotra.