In a Consortium News interview, editor-in-chief of Wikileaks, Kristinn Hraffnsson who visited Assange 2 weeks ago, explained that despite Assange’s condition stabilizing he is still on the hospital ward at Belmarsh prison. (You can watch interview here).
Earlier it was reported he would be returning to his cell in mid-June but the ward must have chose to do otherwise for good reasons. As more info becomes available, I will update.