An article on BBC News Technology that deals with the British gaming industry in general and Little Big Planet and Fable II in particular mentions some of the potential plans Sony and Media Molecule have for Little Big Planet. It is interesting that it is not only the typical sequel that is being discussed but also other products as well as the game being a publishing platform for other brands... the deal with Disney comes to mind.
"Little Big Planet has big potential. Right now it is just a game but the firm, with Sony, are in talks to turn it into a franchise that could mean spin-offs including comics, cartoons, and action figures as well as a publishing platform itself for other brands' content. "
Now all that remains is for Little Big Planet to register big sales and we are likely to see it all come true.