There is a sound rumour around this few days as EO, Variety, Ain't It Cool and Slash Film have all reported casting rumour for Peter Jackson and Guillermo Del Toro's The Hobbit. Brian Cox is apparently "a major contender" for the role of the dwarf.
In case you have not read The Hobbit before, there are 13 dwarves in the book - Fili, Kili, Oin, Gloin (Gimli's dad), Dwalin, Balin, Bifur, Bofur, Bombur, Dori, Nori, Ori and Thorin Oakenshield.
The role of Thorin seems likely. "He fights alongside Gandalf in the goblin tunnels and dies a heroic death at the Battle of the Five Armies. But he's also a bit annoying and rubbish: getting himself captured before anyone else at Mirkwood, making serious diplomatic gaffes at Laketown and throwing a big strop when Bilbo nicks the Arkenstone." - according to EO, refering to the character Thorin.
The other dwarf is likely to be Balin. Balin's tomb was the focus in The Fellowship of the Ring.
For the record, The Hobbit has yet to announce for any casting calls yet. So, Cox in it, is still a rumour after all.