There are very, very, very few things at WDW that, if announced were ending, would cause me to book a last-minute to experience it again. Illuminations is one of those few things. I absolutely adore it. I have seen it live many, many, many times. I watch it online whenever I think to, and the music plays often around here.
I get chills as soon as the lights are blown out, and the tears start soon after. I don't know why it affects me so deeply, but it does. I truly hope it is still there in June. I would buy a ticket to see it, and only that.
FWIW - the other things I would book a last minute for are Spaceship Earth, Splash Mountain, Living with the Land, and Everest...