As Olin mentions in the tweet, you can pre-purchase the DLC right now through Steam. Though you don't strictly need to secure your copy of a digital-only product ahead of time, since there's no concern about scarcity, you do save $1.50 by doing so.
Posted on Jan 27th 2015 8:15AM
Posted on Jan 26th 2015 11:00AM
Posted on Jan 26th 2015 10:00AM