3 big things are scheduled to open in 2017, but April sounds a bit early. What will definitely be new is Rein of Kong (Which already looks amazing) and the completely redone Hulk as well as the new Sapphire Falls hotel. Race through new York with Fallon may be open by the time you get there, but I doubt Fast/Furious will. Wet n Wild shuts down this coming December, so there will be a gap of a few months before Volcano Bay opens up, but no way to tell this far out if it'll be open in April or not. Historically new attractions opened in June, but it really depends on construction and timing.
The unannounced NBA City replacement should also be open, and I wouldn't be surprised for for some other changes to CityWalk as well.