There is no official confirmation till date either from Rajnikanth's "Kabali" producer or from the personal PR of the Superstar about his health condition.
Rumours do maintain that he has fallen ill in USA during a makeup test for Robo 2 and admitted in a super speciality hospital. From last couple of days it is being speculated in media that Rajni, who is on an USA tour along with his family members, is not feeling well and in hospital. But there is no serious confirmation about it.
Meanwhile rumours are also spreading that this is a rumour created to divert attention of fans who are upset that Kabali audio function hasn't happened.