We don't have an exact date yet; it's slated for "Summer 2024," spanning from late May (Memorial Day) to early September (Labor Day).
Memorial Day weekend would be a perfect time to open Tiana’s, we just aren’t 100% that it will be ready by then.
Even if it’s not late May, there is no doubt Disney will want to have this attraction open for the summer crowds, and a June opening may be more realistic.
Whenever Disney does decide to open it, we are quite sure there will be various rounds of preview events like there is for almost ever attraction.
Usually, there are previews first for Disney Cast Members, then Annual Passholders, along with Disney Vacation Club and Club 33 members.