The problem with MCO is that Orlando doesn't want a hub airport. The entire economy is based on tourism and having a hub doesn't help unless the hub is owned by the government.
FLL needs a new tenant who could treat the airport like a hub. Delta has ATL and American has MIA. JetBlue has a presence there, but likely not enough to fill the lost capacity unless it gets a massive capital injection. That leaves United and Southwest.
United is the airline that has the quickest ability to fill the void and has a long term route strategy which can use an airport like FLL, including off-loading some international traffic from IAD.