im not sure at all,but i think it does because have you ever heard of an author who lets you have a sneak peek at the next book, then they never write it? if you go to the infernal devices website it shows another book called "Clockwork Princess". i think even though it doesnt really show the book it does exist somewhere.i mean who gives previews of books and then retires? its just so sad that i cant find it though. i would love to see if tessa and jem do get married or jem falls for wills sister.and if jem does falls for Cecile, than will tessa and will fall for each other?because if they(tessa and will)do get together than will jace herondale(mortal instruments)be their great great great grandson?