HollywoodReporter is listing a few more names that are testing for the role. Kit Harrington is still in the mix who had been mentioned as a front-runner. The new names testing include his Game of Thrones' brother Richard Madden, Luke Evans and Tobey Kebbell.
While WB might be quick to cash-in on the Game of The Thrones heat with Harrington and Madden the other guys could be a better pick. Luke Evans has been making a splash with every big film that involves swords including The Hobbit, Clash of The Titans, Immortals and Three Musketeers. Tobey might be impressing the studio with his performance in Wrath of The Titans as he's rumored to be returning for Clash of The Titans 3.
That being said the studio seems to be testing every actor possible for Arthur. The previous group included Sam Claflin (On Stranger Tides, Snow White And The Huntsman), Dominic
Cooper (Captain America, Devil's Double), Hans Matheson (Sherlock
Holmes, Les Miserables), Jim Sturgess, Ben Walker (Abe Lincoln Vampire Hunter, Paradise
Lost) and Liam Hemsworth (Expendables 2). I'm hoping that we could see these names resurface in supporting roles as there should be plenty of knights and enemy roles to fill.