As i said, inxile did the same with Wasteland 2, also Larian with Divinity Original Sin. Both Games where anounced for Oktober 2013 and in August this where the official release dates for this Games.
Finaly Divinty was release 07/2014 (with content cut out) and Wasteland 2 will maybe released this August, 10 month after the "official" release date.
This official date means nothing to me, sorry.
That is u fortunate that those other developers were unable to deliver on time.
FD is keeping us up to date and in the loop on development. They have a record of over achieving and putting out unexpected content earlier than scheduled. Their track record has to be taken into account. FD is not constrained by a publisher to put out this game by a certain date. They are in complete control on content and delivery time. If they are confident enough in a q4 release date, then I nor any of us here have a legitimate reason to doubt that.