They're putting a lot
of emphasis on the holodeck goggle things, so it's clearly going to have something to do with that. Especially since Kelly used to work for Greystone Industries, the people who came up with that technology as well.
My guess is that it has to do with Zoe. The mission is either to track her down and capture her in order to try to figure out why the Cylons did what they did or find some way to take control of them the same way she did, or Zoe herself has had a change of heart and is reaching out to try to help humanity. Either way, it's going to take place via virtual space.