I wouldn't expect Disney to be sending families home on chartered flights regularly throughout their return to cruising. Way too expensive & Disney doesn't like to waste money, and less customer-friendly alternatives (guest having to pay themselves) would be nightmare PR. I don't think they'll do onboard testing once the law no longer requires it.
Masks, distancing, testing before boarding, I can see that. But not routine onboard testing of asymptomatic passengers. The onboard testing itself creates bad PR because headlines go out saying, "This cruise ship has positive passengers!" So no, Disney isn't going to keep testing everyone during the cruise once it's no longer required.