I read a snippet somewhere that said Eddie and Susannah would not feature in the movie, and I was pretty much done. I'm never going to watch this film.
They were not in the first book, The Gunslinger, either. The plan is for them to appear in future movies, if the first one is a success.
I read, though, that they had cast the role of Sartyr (however you spell it) who is a middle level Low Man who plays a part in the last books, when they've reached End World. I can't see how they would weave in The Dixie Pig or Agul Siento without having introduced the entire ka-tet.
They are introducing viral marketing. Here's the website for the Sombra Corporation. http://www.thesombragroup.com/