I think Hook will fly on his magic parrot to New York (there are now so many ways of travelling from universe to universe- beans, hats, shadows and pegasus feathers.. so why not parrots? he is a pirate afterall)
He will carry a potion for Emma to get her memories restored. They will need her in the Enchanted forest because she has something, that can beat the Wicked Witch -(Water?) Wicked Witch holds the Charmings captive because they came all hero-like to take back the Kingdom that she had seized for herself. Regina and some of the gang managed to escape and live in exile in the forest with Robin Hood and his merry men, for the past year they have been fighting the evil regime of the NEW EVIL Wicked Witch.
The Wicked Witch finds a way to send Regina, some of the gang, Robin Hood and the merry men to Storybrook using the original curse, whats left of it. When they land in Storybrook Rumple someone finds Rumple, whowas stuck in the curse-scroll, he is wounded because of the stabbing but not dead because the DarkOnes magic was bound from the cuff on his wrist. Here they will also meet Emma, now with her memories restored. But Henry, she left in New York with her foster Brother, he does not have his memories back, Emma keeps them from him to keep him out of danger.
Ones again they have to find a way to get from one universe to another, this time they will follow the yellow brick road or drive the yellow bug- just clap twice and say “there is no place like a forest” that will do it, cause everything goes when we have magic..
In the end of the season Emma and Regina will have saved the Enchanted forest and banishes the Wicked Witch by throwing her into lake Nostos wich will send her back where she came from. But bye then it is revealed that the Blue Fairy is up to some sneaky buisness and so, welcome season 4.