Till now there has been no official notice regarding the 4th round of seat allotment process and the commencement of the process. The third round has ended on July 20th, 2019 . Therefore the fourth round will be commencing anytime soon . The fourth round is more tentative to be held from end of July. You can check other details here :

Https://www.google.com/amp/s/engineering.careers360.com/articles/keam-seat-allotment/amp