For Ian, the CMs found out Tuesday afternoon the parks would be closed Wednesday and Thursday and started to let guests know, but official word on the Disney website didn't come until late afternoon (like 5:30ish maybe?). The food and wine food booths closed at 6 on Tuesday as well so they could prep them for the storm. The worst of the storm didn't hit until late Wednesday, there was some rain off and on during the day, but it was calm enough they kept the resort pools open most of the day. So based on that, if they do close, I'd guess they'd make the announcement by tomorrow afternoon.
Hoping for the best for everyone with trips this week and those living down there!