They say grading will take about a month, so if you take the exam May 31 should be graded by end of June, but I'd give 6 weeks, anyhow.
I think it will be really interesting to see how all the testing dates affect the admissions process this year. Will more people retake? Will more people take an earlier exam (in April, we were mostly still in class, by end of May, a lot of people are done w/ finals)? Will people who are totally unprepared take the exam because they can just go take it again in a month?