As wdwgoofeeee said, the May hours were purely an experiment.
In the meantime, Disney has announced E Ride nights for June and July. The scheduling of this extended-hour perk at the MK seems to preclude any changes to the EMH schedule at least through July.
What will happen from August 1st forward is anyone's guess.
We were at WDW during the testing period and were quite happy with the proposed schedule. We are not early risers while on vacation, and had never taken advantage of an early morning EMH. But we were very happy to have the option of staying at MGM until Midnight during our trip.