I'm pretty sure you'll be able to own your own ship, but I don't know if you can cast off and sail around the game.
What other epic RPG's are there? I think I missed a memo.
Upcoming games. Game of Thrones 5/15 - Diablo III 5/15 - The Witcher II 4/17.
Dates are probably subect to change but these are the next games to check out.