The Schedule for bands is now out as well as the final additions to the lineup with 20 new groups added so you can plan whether to get a 1 day /3 day /4 day pass.
The best place to find out is the Womad Website where you can sample some of the music/video of the performers.
The Schedule ( Subject to any changes )
Craftypics's Blog 
the usual suspects, some tried and true, some conservative choices, a few faves and a few newcomers. It’ll be great to catch Lo’Jo for the third time around, looking to Anda Union
and Le Trio Joubran