I hope there isn't a movie because it would be bad. Key parts of the story would end up being cut out. Not to mention the cast. There are some characters with no one who can play them, mostly because of image. The only characters with actors/actresses that look like them are:
Polgara: Catherine Zeta Jones (hands down there is no way anyone else can play her - especially not Angelina Jolie!)
Adara: Natalie Portman (when i saw the picture on this site,
Belgariad - Volontà e Parola sul WEB, it screamed adara)
Sadi: Arnold Vosloo (look at the picture in the link above and you'll see why)