Right now they both do.Sometime in the next few weeks it is expected to go back to just one of the parks and that should be IOA..They don't publish it too far in advance and it is always subject to change at any point
Now - August 2: Islands of Adventure and Universal Studios August 3 - late December (tentatively): Islands of Adventure (Hogwarts Express boarding 30 minutes prior to park opening.)
I called yesterday and asked about my dates (8/14-17) and the guy I talked to told me that both parks were still being offered for EPA... should I check again? LOL