The adaptation of the Chethan Bhagat novel centres on a couple from different states whose parents disapprove of their marriage.
Kapoor told Hindustan Times: "I don't know what transpired between [the makers and Khan]. It's not my concern or business to know that. But when the film came to me, no director or actor was involved.
"Before [director] Sajid Nadiawala came to me, he had already closed the chapter with Shah Rukh Khan."
He added that he had not yet committed to the film, despite having read the novel.
"Of late, Rockstar's promotions have kept me very busy, so I haven't read the script yet. But in the coming month, I will hear it and take a final call."
The Rockstar actor this week said that he does not want to be compared to the three Khans - Aamir, Shah Rukh Khan and Salman.