TrekMovie has an article about Bryan Singer, who says he'd be quite happy if he could do XIII. There is also a link at the end to a EW article about other potential directors, and it's a pretty good list!
Rian Johnson (Brick and Looper)
Duncan Jones (Moon and Source Code)
Josh Trank (Chronicle)
Matt Reeves (Cloverfield and Let Me In, currently working on 2014's Dawn of the Planet of the Apes )
Jonathan Nolan (Chris Nolan’s brother, better known as writer and producer but works with Abrams on Person of Interest and directed one episode, no feature film directing experience)
Neill Blomkamp (District 9, 2013's Elysium)
Edgar Wright (Scott Pilgrim vs. The World, Shaun of the Dead, 2015's Ant-Man )
Joseph Kosinski (Tron: Legacy, 2013's Oblivion, hopes to start work on Tron 3 soon )
Drew Goddard (Cabin in the Woods)
Shane Carruth (2004's Primer, friend of Rian Johnson)
So does anyone jump out at you, ro should they sit tight and wait for JJ to come back from The Galaxy Far, Far, Away?
http://trekmovie.com/2013/03/14/bryan-singer-directing-star-trek-could-be-great-experience/ Is it too early for a Star Trek XIII tag? XD