I don't know how credible this is, but someone on IOA Central posted this:
"My dad's friend works in the parks offices and he said that the soft openings start tomorrow!!! (5-25-10)
This Is TRUE!!!
He told me that most of the employees have to show up at Harry Potter in the morning.
It will most likely be open for like 30 mins to an hour in the mornings. "
http://boards.ioacentral.com/index.php?showtopic=10525&st=2920&p=254213&#entry254213