TJ Mannarino - at the last VIP Lounge panel, when asked if HHN would ever return to IOA - did say it would happen one day, "when the time is right". He was definitely referring to a return to both parks though.
If this were to happen, in my opinion, they have to increase the number of attractions. My wish list: 12 houses (either 6 at each park, or 8 at USF and 4 at IOA), 10 scarezones (6 at USF, 4 at IOA), 4 shows (Bill & Ted in current spot, Rocky Horror at Beetlejuice, Brushwood at Toon Lagoon stage, and something new at Animal Actors stage). Attractions open: Hulk, Spidey, Jurassic Park, Forbidden Journey, Dragons, Rockit, Mummy, JAWS, Simpsons, T2:3D.