For awhile now, Disney has been in a pattern of adding park hours to the calendars on the website on a rolling 180-day basis. You can see them posted through 9/9 since that's 180 days from today. Tomorrow 9/10 will post, etc.
You can 'see' 10 days beyond 180 days if you do this on the website:
- Hover over "My Disney Experience"
- Click "My Itinerary"
- Click "Add Plans" --> Click "Add Parks & Places"
- Change the date at the top
Obviously all park hours that far in advance are subject to change, especially with Disney’s trend of not updating them until much closer to the month in question lately.
Personally, I use last years hours as a framework for what I think this year 'could' look like if I'm looking at something well in advance.
Hope that helps!