I bought ours! So excited. It says "Annual Passholder Premiere: Available from Wednesday, April 15, 2015 to Sunday, April 19, 2015" so maybe we get advance. My DS (who has just arrived at WDW, am jealous) sent me the link, it's on an AP email. "
Only Passholders can prepurchase - Get this cool t-shirt in time for the big 24-hour
Magic Kingdom® event!" I read it as only AP will be allowed to pre-purchase and only those dates so they can get them out to you. HEY, an AP perk, yeah!
OH and it's one of those that the sun makes it change.