Good news the second DLC Advanced Warfare Ascendance release time is 1 am pst time, 4 am est. on March 31st. Which mean you can start downloading it and playing it.
The confirmation comes from Activision support via their twitter account that Advanced Warfare Ascendance release time is 1 am which includes all 4 new maps: Perplex, Site 244, Climate, Chop Shop and Infection Exo zombie mode. For full coverage on DLC follow the next links:
@FleXMasqCA Hey Austin, this content should become available in the Xbox marketplace at 1 AM PST. ^TO
— Activision Support (@ATVIAssist) March 31, 2015