If I sign up to retake in June does that mean they won't make a waitlist decision until after the LSAT?
I think they'd make any waitlist decision regarding your file based on your current information (LSAT score included). I've been debating whether or not to retake too. It's definitely the reason I feel I was waitlisted. However, based on the information available on how waitlists work, I don't think it'd make a difference to retake unless the end product is an amazing/scholarship-worthy score.
I gather they mostly look for waitlisted candidates to replace their initial admits that also fit the initial admit's softs and/or numbers to maintain whatever well-rounded class they're striving for. Additionally, beginning May 15, LSAC "provides participating law schools with periodic reports detailing the number of applicants who have submitted seat deposits or commitments at other participating schools, along with identification of those other schools." The information reported includes names and LSAC account numbers. http://www.lsac.org/jd/apply/whom-to-admit.asp
. While I doubt schools actually rescind their offers, they likely apply pressure to admits and activate their waitlists to compensate.
In short, it's safe to say much of the waitlist movement will happen before June scores are released in July. ...BUTTTT, again, this is a world where rejects can be later offered admission so little is definitive here. Best of luck to you if you do retake!