Seth Kubersky has the details
Effective Tuesday, September 2, 2014, only Universal Studios Florida’s front gates (and not those at Islands of Adventure) will admit eligible guests for early park admission during the off season. Despicable Me and the Diagon Alley attractions will be open at USF during early entry.
In addition, guests with park-to-park tickets may also take the Hogwarts Express from King’s Cross Station to Islands of Adventure to enjoy attractions in The Wizarding World of Harry Pottery – Hogsmeade during the early admission hour. There will be no way to enter IoA during early entry with a single-park ticket.
It seems like a fair compromise for the off-peak season.