The army is now advancing into drug producing areas, and taking on both leftist and rightist rebel groups who protect those areas for the drug gangs. While the rightist rebels (the AUC) are in general agreement about disarming, not all AUC factions have agreed to an exact date that they would disband.
While the leftist rebels are losing militarily, and in terms of public relations, they still hold thousands of kidnapping victims and control about a quarter of the country (all rural areas where drug production is located.) Some of the rebels still have dreams of turning Colombia into a socialist paradise, but most of them are in it for the money, and the money is still coming in. As long as the drug trade thrives, the rebels will get paid, and that enables them to maintain thousands of gunmen.