I think you'll need to wait to see if it's announced.
We were fortunate to be in DW this past week and went to each of the four parks that had EMH. As we left the park we were interviewed by Disney employees and asked what rides, attractions. stores (merchandise bought) we went to during those hours. They indicated EMH would also be done this week (third week in May). We tried to put in the "good word" so they would continue offering EMH.
I guess another deciding factor is personnel needed to keep the park running for these extra hours.