The Faction Pack, planned for release this June as the first piece of single-player DLC, has suffered a slight delay and we're now aiming for a mid-July release on all platforms.
I know those of you who have bought the Season Pass have been eagerly awaiting the first Pack, and I'm really sorry to have to make you wait longer than expected. There were some challenges along the way and we want to make the Faction Pack a solid and unique single-player addition to Metro: Last Light's campaign. I hope you can be patient for a little longer, while we continue to work on making sure it will be worth your while.
The other Packs will be released over the 60 days following the release of the Faction Pack.
As soon as we have a final release date set in stone, we'll share it with you all. There will also be some more screenshots and details in the time to come. Unfortunately, I don't have more info to give you right now.
Having said that, the DLC achievements have been added to Steam and they might give you some ideas of what to expect: http://steamcommunity.com/stats/MetroLastLight/achievements
Last but not least, Metro 2033 fans might appreciate this little tidbit from the Faction Pack: Librarians