I am confused about the LOST tv show.....?!

I am confused about the LOST tv show.....?

I just saw the last episode (I think)....Where at the end of it, Jack and Kate are meeting near the airport and talk...That show as clearly that they have been saved....BUT...I just discovered that in February 2008 the 4th season will be realesed......SO why are they making another season??!!..isn't it over yet???!!! ( Sorry spelling)

Eventually they will get off of the island, but as the other person commented, those were looks into the future, not looks into the past. Thus, there is a lot of story still to be told about what happens to get them off of the island and to make Jack so disillusioned/bitter. There are going to be three more 16 episode seasons before the series ends/all is revealed.