A DLC pack titled Progeny was apparently originally planned for a January 2013 release. This pack was much like Slingshot and featured three new Council missions, a recruitable psi soldier named Annette, and five new achievements. Because of the negative reception to Slingshot on the 2K forums, this was apparently cancelled altogether and is not planned to be released.
The achievements were uploaded to Steam shortly after the release of XCOM: Enemy Unknown, but were removed on 8 Janaury 2013 when Second Wave went live. Before they were taken down, this is what the achievement list looked like:
The Chase Is On - Complete Portent (10 Gamerscore / Bronze Trophy).
Disaster Averted - Complete Deluge (10 Gamerscore / Bronze Trophy).
Great Minds Think Alike - Complete Furies (20 Gamerscore / Silver Trophy).
Saved to Savior - Have your newest ally volunteer for the most difficult duty (30 Gamerscore / Gold Trophy).
No Sweat - Complete Deluge without activating more than 2 valves (30 Gamerscore / Silver Trophy).