Responding to reports that "Once Upon a Time" actor Sebastian Stan would be exiting the show due to "Captain America: The Winter Soldier" commitments (like this one), showrunners/creators Adam Horowitz and Edward Kitsis denied plans to recast the actor during PaleyFest 2013.
Plus, the duo teased details for some of the upcoming season two episodes looking back at the early days of Storybrooke and the revelation of another realm.
To be clear, Kitsis' exact words about Sebastian Stan being replaced were that there were "No plans to recast anyone" according to THR who covered the event. If I could indulge in some completely baseless conjecture here, that doesn't preclude a scenario where there were plans to replace the actor with someone whose schedule might better accommodate the plans for a "Hatter" spinoff. The already sprawling cast of "Once Upon a Time" can do without seeing some of its characters for a few weeks at a time, but you'd have to imagine Disney/ABC would want someone who could commit to the grueling schedule of another series if it should materialize.
As for season two, Horowitz and Kitsis provided the most detail for the 17th episode, "Welcome to Storybrooke" which will be set in 1983 and show us a triumphant Regina adopting Henry after cursing the town. The "Manhattan" episode revealed that Gold knew about a prophecy involving Henry that could destroy the pawn shop owner so maybe that figures into it somehow? We will also see the return of evil Regina, but in a different way than viewers might expect (Clone? Time travel?)
Kitsis and Horowitz also teased a new realm alongside the title of the two-part second season finale: "Second Star to the Right" and "And Straight on 'Til Morning." The latter answers what the former is, I think, although we won't see a character from this land until season three. Earlier this season, Captain Hook said that he'd been to Neverland (although I don't think he named it outright), so it's very likely the new location.