Matthew Lewis will no longer be attending the Florida Supercon because of filming conditions. The official site states:
MATTHEW LEWIS WILL BE UNABLE TO ATTEND THE SHOW DUE TO FILMING COMMITMENTS.
STANISLAV IANEVSKI (VIKTOR KRUM) WILL BE REPLACING HIM ON OUR GUEST LIST
We will still be holding the contest so you can still go and see Stan instead (or whoever you want to see)