That may sound a little tricky, so let me be clear: once Kat and Emmett are finished, we’ll put them up for download. They’ll be totally free for two weeks. The only limit is that you have a two-week window to claim the characters. Once you have Kat and Emmett, they are yours forever. That may sound like a lot to remember, so don’t worry, we’ll be back closer to their release to remind you of all these details.
In other words, it's going to be either paid dlc after those two weeks or they won't be available to anyone anymore. Lame.