Yeah if you buy the box set that comes with the bonus dvd, the series creator says that the last episode of season four (SPOILERS) (SPOILERS) (SPOILERS) (SPOILERS) (SPOILERS) (SPOILERS) (SPOILERS) (SPOILERS) (SPOILERS) (SPOILERS) (SPOILERS) (SPOILERS) (SPOILERS) (SPOILERS) (SPOILERS) (SPOILERS) (SPOILERS) (SPOILERS) (SPOILERS) (SPOILERS) (SPOILERS) (SPOILERS) (SPOILERS) (SPOILERS)
titled the Wedding, implied that the two would be married, (RDJ had not yet been contracted for a fifth season) ... and then he had some "personal issues," which caused him to be unable to do the fifth season... which is why it ended the way it did.