According to the announcement the DLC, aptly titled Ryder White, will add several hours of game play where you will actually play as White. We will all know how it will end, but we will get more information on the overall story of Dead Island as well as what else was going on while the main four were doing their thing. Sounds a lot like the Ada Wong stuff that was added to Resident Evil 4 when it was re-released.
I for one love this kind of DLC. As long as it is really more story and action for the game and not forced "survival maps" with story mixed in. I mean, having stuff like the Catwoman add-on for Arkham City was nice, but it really was Story-Challenge Map-Story. For this DLC I hope it feels just like Dead Island's main game play just with a new character and missions. I don't want to get this and find out that I could have read the story summary online and have been completely satisfied. Given how impressed I was with the game in the first place, I think it will be more of the standard game and not challenge map-ish.
We'll find out here soon though as the DLC will be available on February 1st, 2012. Please don't let me down Deep Silver.