See here. I believe the next opportunity is 6/18. UPDATE: According to Marty Lederman, beginning this week the Court will be issuing opinions on Thursdays as well, so the next opportunity for a ruling in WRTL is 6/14. I’m guessing, however, that this opinion (because it raises difficult issues and because it was argued on the last argument date of the year) won’t be issued until the Court’s last week (likely the week of 6/25).