Some updates from this video from NASA:
- Imagery should be available late May 2013
- Landsat 7 has enough fuel to last until 2016
- LCDM has a 5 year mission, but they are hopeful for a 10 year mission
- Data continuity is the key to this whole deal: "continuity drives landsat"
- High resolution data does not have the temporal resolution as Landsat - via Kass G.
LDCM FAQ here.